Management Strategies

## Network Formation and Analysis of Dengue Complex Network

*Hafiz Abid Mahmood Malik*

#### **Abstract**

Several efforts have been made and are constantly being made to keep the *Aedes aegypti* virus under control. Numerous scholars are involved in the study of medicine, while others are working in computer science and mathematics to model the spread of this disease. This study will help to comprehend how this epidemic sickness behaves. A complex network has been established from the complex dengue phenomenon. We have evaluated dengue network topology by pondering scale-free network properties. The network's resilience in tracking the dengue epidemic is measured by systematically removing nodes and links. The primary hubs of this network are emphasized, and the vulnerability of the network structure has been examined through an in-depth investigation of the dengue virus's spreading behavior. Understanding the intricate web of dengue outbreaks relies heavily on geographic representation. The applied method on the dengue epidemic network and the results will be added as scientific additions to the literature on complex networks. Different network analysis metrics have been applied (closeness centrality, betweenness centrality, eigenvector centrality, network density), and the network's stability has been evaluated. This network is extremely vulnerable to targeted attacks; results showed that after removing 8% of focal hubs, 34% of the network is destroyed.

**Keywords:** vector-borne disease, robustness, dengue vector, scale-free network, complex network metrics

#### **1. Introduction**

Most dengue fever cases have been reported in tropical and subtropical areas. However, reports of its spread to numerous other regions, including Europe, have increased significantly during the past decade. There are around 2.5 billion people who could get dengue fever (DF) or dengue hemorrhagic fever (DHF) [1, 2]. In January 2022, the WHO estimated that there might be between 100 and 400 million new dengue cases worldwide yearly. An estimated 3.9 billion people live in these areas where dengue fever arises (**Figure 1**) [1, 2].

The mosquito is the vector for the dengue virus. Bite transmission occurs mostly due to the *A. aegypti* and *Aedes albopictus* species of mosquitoes, both of which are considered the carrier of the disease [2, 3]. *A. aegypti* is a small, dark mosquito with a silvery white pattern of scales on its body and white bands that may be identified on

**Figure 1.** *World map showing locations with a high risk of dengue fever.*

**Figure 2.** *Dengue vector (*A. aegypti*).*

its legs (**Figure 2**). Most people get bitten by this urban mosquito during dawn and evening [4, 5].

### **1.1 Dengue virus outbreak**

The *A. aegypti* mosquito can spread the dengue virus to humans through a bite. Mostly female *A. aegypti* mosquitoes have been found to carry the dengue virus, which means that females of this type of mosquito may be the superspreader of the disease [4, 6–8]. Female *A. aegypti* have a lifespan of 12–56 days (mean: 34 days) [9, 10]. In order to produce offspring, female *A. aegypti* mosquitoes mate with males and produce offspring by egg-laying; in this way, a male can carry this virus, too. If *A. aegypti* bites any person and that person acquires the dengue virus (DENV), they also become the source of DENV. **Figure 3** [11] depicts the transmission of DENV from an infected *Network Formation and Analysis of Dengue Complex Network DOI: http://dx.doi.org/10.5772/intechopen.109442*

individual to another mosquito (not of the *A. aegypti* species) via a mosquito bite [3, 5]. In addition, dengue symptoms often develop 4–14 days after a mosquito bite. Specifically, the dengue virus's DENV-1, DENV-2, DENV-3, and DENV-4 serotypes have been identified [5, 6, 12]. The infected person's blood can be tested for any of these dengue serotypes. Any individual infected by one of these serotypes is immune to future infection by the same serotype [3, 6, 13].

#### **2. Modeling the dengue epidemic as a two-mode network problem**

The structure of some real-world datasets is naturally bipartite. A key characteristic of this sort of network is that it allows for the partitioning of nodes into two groups (primary and secondary) and the creation of linkages exclusively between nodes in the two groups. To define a bipartite graph, we use the triplet G = (⊤, ⊥, E), where ⊤ is the set of vertices, ⊥ is the set of top edges, E is the list of bottom edges, and E ⊆ ⊤ ⊥. Whereas in traditional graphs, links usually go from one group of nodes to another, in this case, the nodes are in two separate but intersecting sets. If two nodes (of ⊥) in G have at least one neighbor (in ⊤), then they are connected in the ⊥ projection, which is the graph G⊥ = (⊥, E, ⊥). In **Figure 4**, a–d depict the primary set of nodes in the two-mode network, whereas 1–5 represent the secondary set [14].

This study uses a dataset of weekly dengue cases from various nodes (locales) in Selangor, Malaysia, to formalize the epidemic problem as a two-mode network. This

**Figure 4.** *Two-mode networks, illustrated with an example.*

network's primary set of nodes is "localities," whereas the second set is the "number of infected patients in weeks." Two nodes are linked in this network if they have the same number of infected cases within the same week, with the number of cases serving as the link weight. The weighted two-mode network is shown here in **Figure 5**. In Selangor, Malaysia, the weeks are labeled W1, W2, … , W52, and the locations are denoted by the letters PL1, … , GL1, … , and HLL1, … [14, 15].

Limited network analysis metrics can be used for the original, unaltered version of two-mode networks, which is challenging to perform an in-depth analysis [16]. In order to study these kinds of two-way networks, it is common practice first to transform them into a one-mode network.

All of the nodes in a two-mode network are linked by the fortuitous occurrence of weeks, thereby converting the network to a single mode. The actual two-mode network is depicted in **Figure 5**, whereas the one-mode projection is shown in **Figure 6**.

A white node represents the locality in Selangor, while a gray node symbolizes the number of weeks; W1 denotes the first week, W2 the second, W3 the third, W4 the fourth, and W5 the fifth.

Projection is commonly used to transform two-mode networks into single-mode ones [16–18]. Here, we use three different projection techniques—Binary, Sum, and Weighted Newman—to turn a two-mode network into a single-mode one. Based on outcomes, it is determined that the Newman technique is better suited to the dataset under consideration.

**Figure 5.** *A simulation based on an actual dataset.*

#### **Figure 6.**

*The two-mode dengue network is transformed into a one-mode from a geographic perspective, represented in Figure 5.*

Since many real-world networks have weighted information in their linkages, Newman's approach does not account for this fact adequately. The Weighted Newman technique is a generalization of Newman's approach that Opsahl suggests [17–19]. He claims that the weight can be expressed mathematically as Eq. (1).

$$\omega\_{\vec{\eta}} = \sum\_{\vec{p}} \frac{w\_{\vec{p}}}{N\_{\vec{p}} - \mathbf{1}} \tag{1}$$

The link from node *i* to the co-occurrence has a weight of *wip*, where *wij* is the weight between *i* and *j.*

#### **2.1 Dengue epidemic: A network analysis**

Network visualization and analyses of one and two-mode degrees, weighted degree, density, closeness, betweenness, and eigenvector centrality measures are used in this study to examine the dengue outbreak. Primary nodes in the network analysis are the places, whereas secondary nodes are the weeks. As a means of analyzing the predicted results of weighted Newman algorithms, above mentioned network metrics are used.

**Figure 7** is a graph depicting the degree centrality of all nodes in Selangor, Malaysia. All of Selangor's dengue hotspots are plotted along the x-axis. Weighted Newman projection using the centrality metric has been utilized for this purpose. Selangor dengue network nodes with the highest centrality are PL216, PL31, PL137, PL134, HLL161, PL54, HLL84, HLL117, and HLL115, which indicates they have a lot of ties to other nodes. Here, the granularity of these vertices can be observed [15, 20].

From the perspective of degree analysis, the simple degree measure has less relevance in this network and is the crude measure. The binary method does not produce satisfactory outcomes when considering the strength of nodes (weighted degree). With the binary approach, it's clear that the degree and strength of a single mode are identical. The weighted Newman technique (**Figure 8**) produced the out-strength of nodes, which may be read as the overall number of dengue cases

**Figure 7.** *The weighted Newman degree of nodes.*

**Figure 8.** *Gombak network node strengths calculated with the weighted Newman approach.*

reported in certain nodes [21]. On the x-axis, 58 dengue-affected nodes in the Gombak district are illustrated, while the y-axis depicts the strength of these nodes. The strongest network strength was seen at node GL18, corresponding to the highest reported node total of dengue cases (128 cases).

Dengue fever cases were also the second most numerous in GL5, with a total of 121 being reported within the specified time frame. There were four confirmed dengue infections in GL2 and none in GL53. The strength of the two-mode projection and one-mode weighted Newman projection method is the same, suggesting that weighted Newman projection generated more suitable outcomes than Sum and Binary projections.

**Figure 9** is a graph displaying the measured strength of all Selangor nodes. The xaxis shows the total number of dengue hotspots in Selangor (across six districts), while the y-axis displays their relative strength. The weighted Newman projection method was utilized to evaluate the node strength. The Selangor dengue network's strongest nodes are PL120, PL25, PL128, PL121, HLL130, PL31, and HLL64. These hubs are deeply rooted in the dengue epidemic's underlying network.

#### **3. Centralization approaches considered for the dengue network**

The weighted Newman approach is utilized to calculate closeness centrality, which is displayed in **Figure 10** [15, 22, 23]. Eq. (2) is applied in the closeness centrality. As ∝ is set to 0, the shortest path measure is used to determine a node's centrality. Alternatively, if ∝=1, the distance is determined using the link weights. Weighted Newman method results show that GL18, GL1, and GL5 are the three closest values. In other words, these hubs serve as the most direct routes for the dengue virus to spread. Based on the number of reported dengue cases, GL18 is the most important node in the network, whereas GL1, GL5, and GL39 are the most connected. It's proof that there are a lot of dengue virus cases in those areas.

*Network Formation and Analysis of Dengue Complex Network DOI: http://dx.doi.org/10.5772/intechopen.109442*

**Figure 9.** *The weighted Newman method's analysis of the Selangor network's node strengths.*

#### **Figure 10.**

*The Gombak network's weighted Newman centrality in terms of closeness.*

Researchers [17, 24–26] calculated a weighted closeness centrality, provided in Eq. (2).

$$\mathbf{C}\_{\mathbf{C}}^{\mathsf{W}\infty}(\mathbf{i}) = \left[\sum\_{j}^{N} d^{\mathsf{w}\infty}(i, j)\right] \tag{2}$$

*<sup>C</sup><sup>W</sup>*<sup>∝</sup> *<sup>C</sup>* ð Þ<sup>i</sup> is the weighted closeness centrality of node *i,* and <sup>∝</sup> is the tuning parameter. However, *dw*<sup>∝</sup>ð Þ *<sup>i</sup>*, *<sup>j</sup>* is the weighted distance between nodes *<sup>i</sup>* and *<sup>j</sup>*.

**Figure 10** displays the closeness centrality of just the Gombak nodes, while **Figure 11** depicts the closeness centrality of the entire Selangor dengue network.

The x-axis depicts all of the Selangor locations where dengue fever has been confirmed. The closeness centrality measure has been calculated using the weighted Newman projection technique. The nodes with the highest closeness centrality scores in the entire Selangor dengue network are located at PL126, PL31, PL134, PL137, PL127, PL200, SL5, PL28, PL54, and HLL64. This demonstrates that the dengue virus is more likely to propagate from these specific nodes to the rest of the network. As a result, reducing the size of the dengue outbreak requires a concentrated effort at these hubs.

While using the Newman approach, the three closest values are GL18, GL1, and GL5, whereas when using the Sum technique, the top three closest values are GL5, GL18, and GL1. The sum approach of calculating the shortest path has given more weight than the weighted Newman method.

The entire dengue network in Selangor is depicted in **Figure 12** as a betweenness centrality. Weighted Newman analysis was used, with the x-axis representing all dengue-infected nodes in Selangor. The nodes PL126, PL31, and PL137 here have the highest betweenness centrality in the entire Selangor dengue network. This suggests that these three nodes have been crucial in boosting the spread of the epidemic virus across the network.

The generic version of weighted betweenness is Eq. (3) [17–19]:

$$\mathbf{C}\_{\mathcal{B}}^{\boldsymbol{\mu\infty}} = \sum\_{j}^{N} \sum\_{k}^{N} \frac{\mathbf{g}\_{jk}^{\boldsymbol{\mu\infty}}(i)}{\mathbf{g}\_{jk}^{\boldsymbol{\mu\infty}}} \mathbf{j} \neq k \tag{3}$$

*g<sup>w</sup>*<sup>∝</sup> *jk* ð Þ*i* depicts the total number of the weighted shortest paths between two nodes, while *g<sup>w</sup>*<sup>∝</sup> *jk* ð Þ*i* represents the number of those paths that pass by node *i*.

*Network Formation and Analysis of Dengue Complex Network DOI: http://dx.doi.org/10.5772/intechopen.109442*

**Figure 12.** *The weighted Newman betweenness centrality measure applied to the Selangor network.*

**Figure 13.** *Eigenvector centrality measure.*

In **Figure 13**, we see the outcome of applying the weighted Newman projection method to the concept of eigenvector centrality. The centrality score was computed using Eq. (4). The eigenvector centrality (EVC) measure determines the most significant nodes in a network. Moreover, EVC explains how not every link is of the same value. Based on this centrality study, the most significant Selangor dengue network nodes are 272, 270, 275, 276, 273, 219, 271, 73, 142, 175, 143, 178, 242, and 122. These hubs are significant (in terms of high dengue cases); hence, it is recommended that they be taken into account while designing more effective treatments to curb the current dengue epidemic in Selangor. Eq. (4) defines EVC [17, 19, 24, 25].

$$\mathbf{x}\_{i} = \frac{\mathbf{1}}{\lambda} \sum\_{j=1}^{n} A\_{ij} \mathbf{x}\_{j} \tag{4}$$

**Figure 14.** *EVC resembled a power-law form.*

Where xi is the eigenvector centrality of i network, λ is a constant and Aij is the adjacency matrix (Aij = 1 if links i and k exist, and 0 otherwise).

This can be shown in **Figure 14** for the network as a whole using eigenvector centrality, where the power-law form can be observed to indicate the small number of nodes with disproportionately high weights (importance) in comparison to the vast majority of nodes with lower weights [27, 28]. Because more dengue cases appeared at these higher weighted nodes, they should be considered while treating the dengue epidemic network.

#### **3.1 The network density**

If we define a potential link as a connection that could exist between two nodes, then the density of a network is the fraction of these potential links that are actually linked. With a density of 0.52 nodes per node, the network is dense. It's clear from this that most of the network's dengue cases are concentrated in a small subset of nodes. **Figure 15** demonstrates the dense nature of the network. For the Gombak dengue network, the y-axis indicates the likelihood of link weights, while the x-axis displays the link weights themselves.

The density of the nodes in the Gombak dengue network is shown graphically in **Figure 16** as a scatter plot, where the x-axis displays the link weight, and the y-axis shows the total number of linkages. As can be seen, the weight of many nodes is low, while the weight of a select few is significant. If this network is partitioned into distinct clusters, as shown in **Figure 17**, then the clusters will be dense. Therefore, treating these clusters effectively is important to disrupt the global dengue transmission system. The y-axis depicts the connection weight in the Selangor dengue network, while the x-axis displays the total number of linkages.

*Network Formation and Analysis of Dengue Complex Network DOI: http://dx.doi.org/10.5772/intechopen.109442*

**Figure 15.** *The network density.*

**Figure 16.** *The density of nodes.*

#### **4. Dengue network: scale-free aspects**

A few instances of scale-free networks (SFNs) with varying values for the powerlaw exponent are listed in **Table 1**. Observations of the topological structure of complex systems in several areas of biology have been the focus of many recent studies. When Barabasi modeled the World Wide Web and its hypertext links, he introduced the concept of a spectral family network (SFN) with power-law exponents *γin* ¼ 2*:*1 and *γout*t ¼ 2*:*7. Here, γin and γout represent the in-degree and out-degree of the


#### **Table 1.**

*γ for certain representative network systems.*

**Figure 17.** *The density of clusters.*

network, respectively [28, 29]. Scale-free power-law distributions were discovered for this social phenomenon, with *γ<sup>f</sup>* ¼ 3*:*4 for females and *γ<sup>m</sup>* ¼ 3*:*3 for males. Newman modeled scientists as nodes and their scholarly articles as edges in a defined two-mode scientific collaboration network [24, 25]. In this network, the major ties between the two scientists are articles they have co-authored. In the instance of the high-energy physics database, he discovered that the degree distribution of this network follows a power law with the exponent γ = 1.

In **Figure 18**, we see a log–log scale depicting the probability distribution of node strength (the number of dengue cases in various areas of Selangor). If the exponent is roughly near the lower bound of the power-law exponent limit, as shown by the broken line in **Figure 18**, then the network has spatially arranged itself into a scalefree network [15]. As the distribution has a negative slope, the power-law exponent takes on the value �1.9. This probability distribution shows power-law organization across time. Important for determining SFN is the presence of a power-law distribution [15, 24, 27–29].

Moreover, a small number of links carry disproportionately heavy weight relative to the rest. SFN is crucial to addressing the problem of epidemic diseases. If the

*Network Formation and Analysis of Dengue Complex Network DOI: http://dx.doi.org/10.5772/intechopen.109442*

**Figure 18.** *Dengue fever incidence follows a power law distribution* γ *= 1.8.*

**Figure 19.** *Node strength by using Newman projection.*

epidemic diseases are SFN, this network topology will be more effective in stopping them. In contrast to the random network, targeted attacks can take out central nodes.

The distribution of node strengths reveals the general behavior of the network's strength, which is the weighted degree of dengue cases at each node.

The node strength of the weighted Newman projection is depicted in **Figure 19**; the x-axis depicts the strength of linkages, while the y-axis shows the probability distribution of link strengths. The network's geographical organization resembles a power-law distribution, as represented by the line on a declining curve.

**Figure 20** shows connection strength and probability distribution on the x- and y-axes, respectively. It's important to note that the logarithmic scale is used here.

**Figure 20.** *Node strength of Sum projection.*

**Figure 21.** *Weight of links.*

A power-law distribution can be seen in the network's geographic organization, as represented by the trendline on the decreasing curve. As this graph demonstrates, however, the dengue virus particularly hits hard only a small subset of nodes. Heavy tails and right skews were seen in the link weight probability distribution.

In **Figure 21**, we see a representation of link strength as a linear function of link weight, where the x-axis indicates the total number of links, and the y-axis reflects the strength of individual ties. It shows that a small number of links in this two-way network have disproportionately impacted the entire network. There are only a handful of major hubs where dengue fever has been widely reported.

#### **4.1 Vulnerability of nodes shown on actual map**

Fifty-eight affected nodes are detected in Gombak, Selangor. The dengue-affected locations are shown on the Google Map, highlighting the Gombak area. In **Figure 22**, the Gombak boundary is shown with a curvy red line spotted with a red arrow, and the dengue-affected areas of Gombak are shown in small circles labeled GL1 (Gombak Locality 1) until GL58. Dengue hotspots are displayed here as distinct groupings on the map. GL15 and GL18 are the primary nodes in this cluster regarding the total number of dengue cases reported. Other clusters include GL19, GL20, GL22, GL29, GL6, GL15, GL16, and GL17 [23]. The nodes GL23, GL39, GL40, GL45, GL01, GL38GL53, and GL52 form a second cluster, with GL01 and GL39 serving as its primary hubs. GL05 is the central core of this cluster. However, other clusters such as GL49, GL50, GL 7, GL5, GL10, and GL54 are also visible.

Using a red circle, we have drawn attention to the five major centers (in terms of high dengue-affected cases) in **Figure 23**. These five nodes account for 8% of Gombak's total dengue network. The nodes GL01, GL5, GL15, GL18, and GL39 are colored red. Taking the total number of dengue cases into account, it becomes clear that these are the epicenters that must be addressed to control the spread of the disease. A higher-than-usual number of dengue cases indicate that there are more *A. aegypti* in the area. In addition, these nodes play a crucial role in dismantling clusters, allowing for the elimination of particularly large clusters from the network as a whole.

If this 8% of the network's nodes, symbolized by the green circles in **Figure 24**, are fixed or removed from the network in the future, then this destroys 34% of the dengue network. This is a good illustration of the effectiveness of a targeted attack that is more useful in a scale-free network than a random one.

**Figure 22.** *Gombak dengue map.*

**Figure 23.**

*Targeted 8% nodes (red-colored localities).*

**Figure 24.** *Targeted 8% of nodes are recovered/removed/treated.*

After the targeted elimination of 8% of nodes in the dengue epidemic network from **Figure 24**, the remaining 66% of network is shown on the real map in **Figure 25**. Other nodes in the network that serve as focal hubs have also been identified. This strategy can slow or prevent the spread of the dengue virus. It has been analyzed that a *Network Formation and Analysis of Dengue Complex Network DOI: http://dx.doi.org/10.5772/intechopen.109442*

**Figure 25.** *Remaining 66% of network.*

5% targeted approach created equivalent consequences to 65% of random attacks on the network. Accordingly, rather than dismissing this network as random, it should be treated as a targeted attack that is more powerful in the scale-free network.

#### **5. Conclusion**

Dengue fever poses a significant global burden and new challenge to health policymakers worldwide. Despite the many attempts made to combat *Aedes aegypti* and its detrimental impacts on humans, no definitive victories have been achieved yet, as mentioned in the literature review. We have used empirical methods to describe and evaluate the dengue outbreak as a complex network. The dengue epidemic is established to be a scale-free network using network analysis metrics and robustness under the targeted attacks. The results demonstrated that a dengue epidemic network is vulnerable if they adhere to a scale-free network structure.

Furthermore, the study results indicated that eliminating a small percentage of focal hubs destroyed a big part of the network, demonstrating a feature of scale-free networks. The findings revealed that 8% of network nodes, that is, GL01, GL5, GL15, GL18, and GL39, were removed from the Gombak network, resulting in the destruction of 34% of the total network. Dengue network modeling and proof as a scale-free network will contribute to the body of knowledge on complex networks.

#### **Conflict of interest**

The authors declare no conflict of interest.

### **Author details**

Hafiz Abid Mahmood Malik Arab Open University, Aali, Bahrain

Address all correspondence to: hafiz.malik@aou.org.bh

© 2023 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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## Mapping the Dengue Cases Distribution with Google Earth Pro™, Geocoding Attributes Tables

*Juan Gabriel Ledezma Acevedo*

#### **Abstract**

When the epidemiologists need to analyze the distribution of cases in a study or the outbreak trend of cases over time, usually they use graphics for representing the magnitude over time (by incidence and prevalence), tables for describing the variables of the affected people (by race, age, sex, weight, and social condition), and maps describing the spread of places and distribution over time. The technological advances gives most people access to latitude and longitude in smartphones and easy access to a GIS-like free software such as Google Earth™ (GE), an intuitive and effective program for a fast map of the case addresses geocoded, an easy way to display layers imported from formats like Shapefiles extension, and showing over those layers Excel tables with the patient variables and geocoded data from the sheet. Besides, it gives the availability of saving the spatial data with the variables, in files that can be mailed and displayed in smartphones and PCs with Google Earth installed and with outcomes that have a format compatible to GIS classic software.

**Keywords:** epidemiology, spatial analysis, mapping, geocoded attribute tables, arbovirus, dengue, google earth pro™, geographic information system

#### **1. Introduction**

Geographic information systems (GISs) are commonly used by professionals for analysis of geocoded data over maps. But these software are for specialized and trained personnel. Some of them like Arc Gis™ are licensed and have an important economic cost; some other like Quantum Gis™ are open source but not easy to use without appropriate training; some other like EpiInfo™ allows to create variable income of cases and associate them with the geocoded data.

But Google Earth Pro™ has proven to have an extra advantage over classic GIS software. It has the possibility for searching places by typing the name while using it for mapping and also by copying the geocoded data from the search bar placemark, which appears on the surface of earth satellite imagery or the commercial sites in search. So, it is very easy to locate reference places like parks, hospitals, or buildings and approach the address of a patient's home, and this way, the epidemiologist can make the mapping free and easy geocoding of the attribute of the table linked to the corresponding marks in the map.

In 2013, the author of this chapter worked as an epidemic surveillance professional for the government health ministry and tried to give a better representation of the affected places in a rural town, Nandayure, located in the Guanacaste region of Costa Rica, Central America. That region is one of the 3 regions from Costa Rica that usually concentrates over 80% of dengue cases among 9 regions of the public health system [1] and is endemic for dengue fever and other arthropod-borne viruses like chikungunya and Zika, but not for malaria or yellow fever.

So the author of this chapter reported the findings to the director of the office and with another office partner created an original paper of the new case of use of GE™ for mapping cases of dengue, with the combination of excel table of attributes, just like joint function in GIS classic programs but easier.

The occurrence of outbreaks motivates epidemic interventions, in order to control the spread of the viruses and to avoid more neighborhoods and other towns from getting affected. So, the map of the incidence every day or week permitted to make an analysis of the magnitude of the spread for targeting a more extensive application of insecticides [2], and this way it helped to have a lower cost and more effective control of the adult mosquitoes, near the affected person.

The incidence of arbovirus-infected patients in a medical center implicates a report ticket submission to the surveillance in 24 hours after medical assistance in Costa Rica's health system, because this establishes sanitary legislation and regulations [3, 4], and 48 hours after ticket reception the vector control health workers must start investigation, looking for breeding sites of *Aedes sp* and applying insecticide in the house and surrounding houses. Mapping cases of dengue fever is important and necessary for distribution surveillance. But is not acceptable by croquis, or drawings that lack of adequate scale. Especially when everyone has access to satellite imagery free and easy with GE™.

The use of GE™ for the mapping of cases became a case study, and the advantages found in the software were important for improving the quality of representing outbreak advance and control. Because of the images that were offered by the software, it made easier it to save and compare the data over time. Intuitive interface made easy to mark a place with a click of the mouse, and right click permitted us to see the altitude, latitude, and longitude of that mark; rename, cut, and copy; change position; add an image; and so on, just like moving a file in the desktop screen of a PC. The case study becomes a case of use, when the software is commonly used for technical reports, with maps showing the satellite image quality, with title, legend, cardinal points, and scale, by only clicking on a tool bar at the bottom.

At the end of 3 years of use, the author realized that is it possible to take a mark or a group of placemarks from the layer panel, at the left side of GE screen, and convert them it into an Excel sheet, and it is possible to do the opposite: importing an excel table with typed latitudes and longitudes, having as a result a geocoded mapping of dengue patients, showing the coordinates as marks on the satellite images map of Google software. The union of these data from the Excel of attributes with the marks coordinates obtained from health care givers about infected people has an improved database in three dimensions, because it includes time space and person variables at the same time.

All data and variables like the onset of symptoms, address geocoded, and the characteristics of the persons like age, sex, name, date of birth, ID number are provided in a file .text extension that allows to import the data and show them on Google Earth. The label is chosen from the attributes table with the import procedure and with an intuitive navigation as simple as a left click and shows all the data from the patients'

*Mapping the Dengue Cases Distribution with Google Earth Pro™, Geocoding Attributes Tables DOI: http://dx.doi.org/10.5772/intechopen.109602*

information, and the imported sheet can be saved as a file easy to send as an email attachment and has been proven to be compatible with classic GIS software since 2008 [5].

And that is useful for adding a higher quality map, with marks representing data important for analyzing trends, showing the affected area on a global scale where it is possible to zoom in and out to get a satellite quality view of the streets, relief, and flora. And with great accuracy, it is very easy to get to the roof of a patient's house just by scrolling with the mouse.

A better way for reporting the epidemic distribution of patients' incidence, with layers that can be displayed sequential weekly or monthly, is by just saving different files according to the needs; this way the epidemiologist can explain the location where the outbreak started and how it increases and spreads, to focus efficiently on the intervention and the resources for the decision makers.

Mapping with GE™ began as a case of use for displaying marks representing sickness distribution in a satellite picture from a visor named GE and became a GIS-like layer viewer, with information about patients who had dengue fever, geocoding the houses where they live for a better epidemic surveillance, mapping and analyzing data according to the neighborhood population, altitude, temperature, and urban population density. That case of use of a free software became an original article [6].

#### **2. Using Google Earth Pro™ (GEPro) as a geographic information system**

A spot map is used to display the location of each health-related state or event that occurs in a defined place and time. With rare diseases or outbreaks, each point on the map represents a case. An area map may also be used, which indicates the number or rate of a health-related state or event by place, using different colors or shadings to represent the various levels of the disease, event, or behavior [7].

#### **2.1 GIS + epidemiology**

The spatial analysis of epidemic phenomena like uniting space, time, and person with all important variables is the backbone for public health.

The time of the year an outbreak starts is important, including when the increase of the incidence is already known previously, like seasonal flu. And weather-related conditions such as temperature, tropical rainy season, and altitude have influence over vector-transmitted diseases; dengue fever is a seasonal and environment-related incidence sickness [8].

These geographic terms are increasingly finding their way into the epidemiologic literature, as advances in the GIS technology make it ever easier to connect spatially referenced physical and social phenomena to population patterns of health, disease, and well-being. Modern geography allows us to understand the space and how its singular environment has an influence over countries, regions, and places [9]. Matching the spatial distribution of cases and outbreaks to the individual, demographic, social and geographic particularities [10].

The variables about a person and its condition are important; for example, taking care of a pregnant woman in a Zika outbreak is fundamental for avoiding congenital abnormalities; some strategies include giving nets to pregnant women [11, 12].

The unstoppable actualization of geographic information software and the free access to satellite imagery make it easier to epidemiologically apply the advantages. Besides the description or illustration of one condition, the selection of more affected areas must be the focus for the prevention plans and interventions and for the search of possible solutions to the etiology of the condition [13].

The burden of the disease, the global impact, and the vector-transmitted arbovirus become medullar for the necessary increase of the use for satellite imagery. And the advantages offered by GIS have been promoted by the World Health Organization [14] for the prevention of and attention to dengue.

Pan-American health organizations have promoted the use of GIS as a part of their projects to strengthen the capacities of the governments from North, Central, and South America [15].

Nevertheless, it is uncommon to use a GIS for the "place"-related analysis, and usually, rates of people over place are displayed like the entire geographic area in a code of colors that represents level of affection according to those rates. While some health systems in poor developing countries still have whiteboard croquis, some countries have control over the information of patients for preventing epidemics very strictly, by the use of artificial intelligence like by China during the Covid-19 pandemic. One of the experiences of the use of Google Earth for epidemic surveillance was the controlled isolation of Covid-19 infected people; many countries established quarantines and isolations, and some of them developed software for the geocoded control of the isolated people for the respect of isolations and quarantines [16].

Improving urban Aedes control and achieving a measurable impact on dengue virus transmission require a reformulation of current strategies and a stronger focus on the adult mosquitoes that actually transmit the disease, both lowering vector abundance and preventing human–vector contact [17].

In Costa Rica, surveillance of dengue includes the intradomicile and extradomicile insecticide application for the house of a person diagnosed as likely dengue or confirmed dengue, and sometimes the place of work, schools, and public institutions are also treated. There is control o larval, adult, and breeding sites.

Where a case of dengue reported stays the most duration of time, some surrounding houses are also treated, for the protection against the possible infected mosquitoes. If the person has been in medical assistance, the surveillance structure of the mandatory public health system laws and guidelines include the case report and investigation about the places visited 15 days back. And in the case of an outbreak, mapping the cases through the weeks is mandatory until the outbreak is under control [18]. But mapping is not usually as good as the high level of quality of geocoded satellite imagery as Google Earth offers.

Dengue fever is a vector-transmitted disease. Dengue transmission occurs through an insect vector, predominantly *Aedes aegytpi* but also *Aedes albopictus*. Environmental parameters, especially temperature and precipitation, affect the demography and behavior of these vectors, making dengue an obvious candidate to investigate the impact of climate on the disease [19].

In 2008, a group of epidemiologists concluded in a *Bulletin of the World Health Organization* about the importance of taking advantage of Google Earth uses and explained how advanced and costly concepts for disease surveillance could turn into an opportunity to apply low-cost tools and solutions. GE™ proved to be an excellent way to develop great alternatives for improving public health by the urban visualized spatial patterns of vector-borne diseases, creating maps showing the location of blocks with dengue cases reported in 2006 for Chetumal and Merida, México. They showed how to draw blocks made with polygons that would be colored for demonstrating where the cases of dengue affected that block. And they added marks *Mapping the Dengue Cases Distribution with Google Earth Pro™, Geocoding Attributes Tables DOI: http://dx.doi.org/10.5772/intechopen.109602*

for labeling infrastructure. But they described limited access then, because of limited internet access in developing countries and rural images that were of poor quality at that time. But this limitation with regard to rural imagery quality changed in 2015 after GEPro™ became free to access [20].

Now instead, the case of use becomes an advantageous technique for any user who requires the map to show the distribution of any Excel sheet on satellite imagery quality. The next is an explanation about the step-by-step process for mapping the entire Excel with attributes and the geocoded address, based on the experience of the place distribution analysis obtained after mapping for each patient reported as a case of dengue fever to the surveillance system, in a rural place from Costa Rica.

To obtain a detailed mapping with all the cases represented over the satellite image, keep all the variables originally in the sheet of the workbook. And for any Excel with geocoded data, patients' workbook can be imported from Google Earth. A sheet with geocoded data of hospitals, or neighborhoods, or houses covered by the medical or insurance service shows the details of each variable of interest.

#### **2.2 Is Google Earth™ an SIG?**

#### *2.2.1 Software description*

The program starts with an interactive globe, and with the scrolling of the mouse, it can easily zoom in to any point on the surface of the earth, with a high level of detail and accuracy. In the program, the view shows relief; can measure routes and distances between two points; generate polygons and area measurements, circle radius, areas, circumference, and diameters; open other layers; and import other formats like shape files. The layer panel, to the left and down of the screen, lets activate roads, places, photos, announcements, 3D buildings, borders, and labels [21]. But the most important difference or advantage over classic GIS programs is the option to search for a place or direction.

GEPro™ is a layer viewer that could not be considered an authentic GIS, because some spatial analysis tools are not available, neither layer editions nor access to attribute tables. But it is becoming the key for the public health map of events [22]. Besides that, it offers high-quality satellite imagery and powerful search tools, for commercial infrastructure, public infrastructure, and places from local territorial division.

But it is not available to filter marks from a group of placemarks, for creating a new layer based on attributes, like filtering on the classic GIS layer. Hence, if a user has a layer in GE™ that shows the addresses of the dengue cases that have occurred in 1 year, it is not possible to select a filter and create a new layer with only 3 months. The way to create that filtered layer would be to filter in the Excel the 1 year table of attributes, copy in a new Excel only the information from the filter, save the Excel in a (Tab delimited)(\*.txt). format, and import the new layer from the GE software.

The procedure in this chapter shows the steps of a case of use where an Excel attribute sheet is imported as a text sheet from a workbook with latitude and longitude to GEPro™. The user has access to the variable tables by clicking the placemarks; the marks can show individually the information from the original Excel attribute table when it is left clicked on the placemark.

But if you need to convert a group of marks that you obtained from GPS into an Excel file, it is possible also by another case of use of GEPro™, moving all the points or marks into a folder in the left viewer, saving as a KML file, and then converting KML into an Excel workbook.

With a right click on the left panel of places for creating a new folder, the placemarks can be moved with the left click to the folder or copied the same way a folder is created and files are moved in the screen of windows; cut and paste with a right click for the mark you will move to that folder created in the placemarks panel.

And with the same right click, save the file into a KML or KMZ format, and that file extension can be used for creating the Excel workbook with all the latitude and longitude data, very easily, by accessing the free Geodata converter on the internet [23]. Then, import the KML or KMZ file saved and convert it into an Excel workbook with coordinates.

There are 3 versions of Google Earth™: normal, Pro, and enterprise open source; all of them are free. But the one described here is Google Earth Pro™. The standard version allows comment maps and creates files KML format, placemarks, polygon, lines, routes, and show layers of maps. The Pro was designed for commercial and professional use but became freely available in 2015 and incorporated improvements about import of maps and digital layers in different formats. The Pro version allows up to 2500 marks sharing and improved the resolution for all images and maps in even rural areas (**Figure 1**), thus enabling the user to explore demographic data, print screen, and make movies off connection [20].

Google Earth frame is based on satellite imagery (Landsat, SPOT, Quickbird) and aerial photography; both of these are periodically actualized. Satellite imagery is full of quality and has great accuracy; thus, a high resolution of Google Earth Pro is guaranteed, the interval of error goes from 0.6 to 1.3 meters [24]. By the year 2016, Google Earth image resolution improved even more, due to Landsat 8th imagery [25].

Some authors indicate Google Earth is not a GIS; maybe it is not a classic one like ArcGis™ or QGis open source, but it is compatible with them because the outcome format KML can be opened on classic GIS software. And it has advantages over classic ones, because it is easy to access, reliable, fast, portable, free, and intuitive and offers powerful search.

#### **Figure 1.**

*A scale map of a rural neighborhood created from Google Earth Pro™. Figure created by the author of this chapter.*

*Mapping the Dengue Cases Distribution with Google Earth Pro™, Geocoding Attributes Tables DOI: http://dx.doi.org/10.5772/intechopen.109602*

#### **3. Procedure concerns for mapping the Excel with geocoded addresses**

#### **3.1 Installation**

First of all, one must install Google Earth Pro™ by downloading the program from the official website [26].

Once you start using it, it is very important to go to the tools, select options, and change the Show Lat/Long options, choosing decimal degrees, because the program begins when it opens the first time, showing degrees in minutes and seconds; this is a format that is not compatible with most of the cellular coordinates that often are shared by message services like WhatsApp location sharing.

#### **3.2 Excel considerations**

The second basic concern is to check the Excel workbook, which must have only one sheet, because the import of a file is only for a singular sheet. When the Excel has the latitude and longitude separated by comma, the file imported in GEPro™ will have a problem for the decimal reading; thus, the decimal must be separated by a point. For an easier and faster change, go to the search option in Excel and choose the replace option; there you have to type a comma for the search and type a point as the replace; it is going to change all the comma-separated decimal to point-separated ones (Video 1 available at: https://youtu.be/29BR7NM52XY).

#### **3.3 Mapping patient's address in Google Earth Pro™**

Epidemiologists are daily familiarized to databases that show variables of the victims or affected cases; most of those data can be exported to other formats and there is always an Excel workbook option outcome, which contains the list of patient information like ID, date of birth, symptom onset date, sex, work, address, and more.

But if the direction is from a place the user does not know or is located in another city, or if the epidemiologist mapping that case is new in the town, the map of cases could be a big deal. In this case, the user of GEPro™ can take the address and type in the Google Earth search panel the name of the building where the person reported to be living at the moment of the medical attention or the coordinates sent from a WhatsApp message of the patient's location.

For example, if the address is 600 meters north from the church, it is so easy to place a mark by typing the name of that church in search option, then with the rule measure, the 600 meters in the north direction guided by the cardinal points is shown on the screen. The rule is one of the most important in the tool bar, which helps to place a mark based on the address.

In the approximated measurement, the user sets the placemark and copies the coordinates of the latitude and longitude, so these values must be pasted to the latitude and longitude column in the Excel, with a negative sign in the case of western hemisphere and southern hemisphere. This way, the epidemiologist goes on to add more geocoded addresses to the Excel due to the cases.

#### **3.4 Correcting an address**

Sometimes, trying to find the house of the person with dengue fever symptoms, for the necessary breeding site assessment and insecticide intervention, can be

difficult because the direction given by the person to the medical service was not good enough because of missing information, or wrong cardinal point reference, or not being the current address anymore. And the health worker can ask the patient for the coordinates of the current address by cellular phone to relocate the geocoded position of that house. That way the arbovirus assessment can be more accurate, and the change in the address of patients can be done right and easy. Just change the data of the latitude and longitude columns from the excel sheet and this way correct the wrong address and save the workbook for importing again from GE™.

An experience of isolation and control of transmitted disease with geocoded data, occurred when a tourist visited for vacations during pandemic between 2020 and 2021. Before leaving the country it was necessary a negative test for covid, but if the person tested positive to Covid-19, that tourist had to stay more days in the country for isolation, and sometimes needed to find another place to move, because the next days, the room would be reserved for other tourists, so the Covid-positive person sometimes had to change the place of isolation.

In this case, the coordination with the surveillance system may include the patient asking for permission or communicating to the professional epidemiologist of the surveillance system to move to another place. And one of the ways to confirm the new location of isolation could be by sending a mail or message to confirm the new place coordinates to continue isolation; the person can be asked if they agree to send a message with the location from the cellular phone through a WhatsApp message or email. Sending location before getting out of the room and when arriving to the next room or hotel can help the health system give better and faster assessment in the case of an emergency.

#### **3.5 Importing data from Google Earth**

The Excel workbook must have only one sheet, and for the import of the data, we have to save that workbook as a copy, in a text format that looks this way: (Tab delimited)(\*.txt). That file is the one for import; in Google Earth Pro™, go to the tool bar, File/Import; there the file will be shown while selecting the generic text \*.txt \*.csv format that corresponds to the name of the workbook tab delimited saved.

When all the addresses are geocoded with corresponding latitude and longitude for each case in the Excel workbook, it is very important to fill all empty or missing data of the sheet with alternative words, like typing null, 9999, empty, missing, or any word that completes that missing data, because empty cells can make the display of variables misplaced, when importing the workbook from Google Earth.

#### **3.6 Creating layers with filtered data from Excel sheet**

If epidemiologists, health providers, or any user has all yearly data of dengue cases in an Excel workbook and wants to create a layer with only one-month cases of dengue, to see a one-month layer of marks, one must filter the month in Excel, copy the elements, and paste them on another workbook. And save this new workbook as a layer of cases with the only filtered month as another text sheet or (Tab delimited)(\*.txt).

#### **3.7 Opening the layer of marks in Google Earth Pro™ and final steps for the template**

When importing, the user must select File/Import/and chose import the (generic text \*.txt \*.csv) extension; suddenly, a window appears named Import wizard. The user must check or select the delimited tab bottom, and then press next. In the next

#### *Mapping the Dengue Cases Distribution with Google Earth Pro™, Geocoding Attributes Tables DOI: http://dx.doi.org/10.5772/intechopen.109602*

window, user must check or select the latitude field correspond to the column with latitude data, and the same for longitude. Frequently, the latitude is the (Y) labeled column and the longitude is the (X) column of data. Then, user must press the finish bottom and create the template style, at this step, it is very important to choose the label selected column, could be names, or maybe the number of the case, in the order they became sick. The user can choose the label to display over each point and can choose the color and the figure for the marks. Having as a result the .kst extension file to save. It appears at the left panel as a GE™ world symbol that contains the marks, to see the marks individually, must double click the GE™ world symbol that contains a folder with all marks. And finally, there is the layer of geocoded addresses, that represent the cases imported from Excel with all attributes (Video 1 available at: https://youtu.be/29BR7NM52XY).

It is very important to know that layers like a .shape extension files can be imported from GEPro™, so the atlas with borders, layers of cities, rivers, and more can be imported and become part of the map with the distribution of cases, represented by placemarks.

#### **3.8 Sending the file by mail and format compatible to GIS programs**

Any mark, polygon, route, layer, or group of them can be saved as a file and exported in formats compatible to classic GIS apps and programs; just save the place or mark or group of marks. The format is KML or KMZ file, which can be sent by mail to a person with GE™ or classic GIS preferred program installed on PC, or tablet, or phone. The person will be able to see the saved information display instantaneously.

The public health systems and databases should incorporate that geocoded data for the surveillance of infectious diseases transmission, not only for arboviruses vector-transmitted diseases but also for respiratory and several infections that become of interest, mainly those under international surveillance. For example, the next figure is a print screen of GE™ view, that shows marks with a label, that is the number of the case, and left clicking the mark, displays attributes or information from dengue patient number 40 reported by the medical service from a rural town of Costa Rica, that occurred on 2022 (**Figure 2**).

#### **Figure 2.**

*Print screen of left click over a placemark labeled 40, which represents the 40th case of dengue with attributes shown, numbers arranged by symptom onset. Figure created by the author of the chapter.*

#### **4. Conclusions**

Any epidemiologist can map the cases of vector-transmitted diseases with an Excel attributes sheet and geocoded addresses, importing the data from Google Earth Pro™, for a better space, time, and person analysis that is free and easy.

### **Acknowledgements**

To the Ministry of health of Costa Rica, where the science, the sanitary legislation, and health regulations have permitted to preserve care of the public health, by the emission of health politics that establish the guidelines for the attention of patients identified by public and private health providers, and for the actions that allow the control of epidemics, and for the opportunities offered by this governmental institution for professional growth, for a great epidemical surveillance system.

### **Conflict of interest**

"The author declares no conflict of interest."

#### **Notes/thanks/other declarations**

Thanks to the public education of Costa Rica. Thanks to my family.

### **Video materials**

Video 1. Mapping an excel sheet with geocoded data on Google Earth Pro, for epidemic surveillance. Created by the author for a better interactive user's guide. Available from: https://youtu.be/29BR7NM52XY.

### **Acronyms and abbreviations**


*Mapping the Dengue Cases Distribution with Google Earth Pro™, Geocoding Attributes Tables DOI: http://dx.doi.org/10.5772/intechopen.109602*

#### **Author details**

Juan Gabriel Ledezma Acevedo Ministry of Health, Nicoya Peninsula, Central Pacific Region in Puntarenas, Costa Rica

\*Address all correspondence to: juan.ledezma@misalud.go.cr

© 2023 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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*Mapping the Dengue Cases Distribution with Google Earth Pro™, Geocoding Attributes Tables DOI: http://dx.doi.org/10.5772/intechopen.109602*

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[14] World Health Organization. La Implementación de DengueNet en las Américas. Informe de una reunión de OMS/OPS/CDC. 2003. Available from: https://apps.who.int/iris/bitstream/ handle/10665/67925/WHO\_CDS\_CSR\_ GAR\_2003.8\_spa.pdf?sequence=1. [Accessed: 2022-12-12]

[15] Organización Panamericana de la Salud. Sistemas de Información Geográfica en Salud Pública (SIG-SP). Available from: https://www.paho.org/ es/documentos/programa-regionalaccion-demostracion-alternativassostenibles-para-control-vectores [Accessed: 2022-12-12]

[16] Ausma Bernot, et al. China's 'surveillance creep': How big data COVID monitoring could be used to control people post-pandemic. August 31, 2021 1.32am BST. Available from: https://theconversation.com/ chinas-surveillance-creep-how-bigdata-covid-monitoring-could-be-usedto-control-people-post-pandemic-164788 [Accessed: 2022-12-12]

[17] Sperança M. Insecticide-treated house screens to reduce infestations of dengue vectors. A. Dengue - Immunopathology and Control Strategies [Internet. London: IntechOpen; 2017 Available from: https://www.intechopen. com/chapters/54879

[18] Ministerio de Salud. Chikungunya: Protocolo de vigilancia y manejo clínico 2014. San José, Costa Rica. pp. 15-20. Available from: https://repositorio. binasss.sa.cr/xmlui/handle/20.500.1 1764/3719#:~:text=El%20Grupo%20 Técnico%20Nacional%20de%20 Enfermedades%20Vectoriales%2C%20 conducido,y%20promoción%20de%20 la%20salud%20y%20comunicación%20 social. [Accessed: 2022-12-12]

[19] Díaz-Vélez C, et al. Situation of dengue after the phenomenon of the Coastal El Niño. From dengue fever

in a one health perspective. 2020. DOI: 10.5772/intechopen.92095. Available from: https://www.intechopen.com/ chapters/73080 [Accessed: 2022-12-12]

[20] Morales A. Google Earth Pro un visor de capas gratuito, ¿También un GIS?" Available from: http://mappinggis. com/2015/02/google-earth-pro-un-visorde-capas-gratuito-tambien-un-gis/. [Accessed: 2022-12-12]

[21] Carralero N. Google Earth y el trabajo por competencias en el aula de Informática. Revista Digital Sociedad de la Información N° 36 –Julio Available from: http://www. sociedadelainformacion.com/36/ GoogleEarthCompetencias.pdf [Accessed: 2022-12-12]

[22] Kamadjeu R. Tracking the polio virus down the Congo River: A case study on the use of Google Earth™ in public health planning and mapping. International Journal of Health Geographics. 2009;**8**(4):1-2. DOI: 10.1186/1476-072X-8-4. Available from: https://ij-healthgeographics. biomedcentral.com/articles/10.1186/1476- 072X-8-4 [Accessed: 2022-12-12]

[23] MyGeodata converter. Online GIS/CAD Data Conversion and Transformation Tool. Copyright © 2022 GeoCzech, Inc. Available from: https:// mygeodata.cloud/converter/kml-to-xlsx [Accessed: 2022-12-12]

[24] Corbelle E, Gil M, Armesto J, Rego T. La escala cartográfica de la imagen de satélite. Caso particular de las imágenes Ikonos y QuickBird. Revista de Teledetección. 2006;**26**:18-24. Available from: http://www.aet.org.es/revistas/ revista26/AET26-02.pdf [Accessed: 2022-12-12]

[25] CNN en español. Google Earth tendrá imágenes de alta resolución. Available from: https://cnnespanol.cnn. com/2016/06/29/google-earth-acabade-lograr-una-gran-mejora/. [Accessed: 2022-12-12]

[26] Google Earth Pro. Available from: https://www.google.com/earth/ versions/#download-pro [Accessed: 2022-12-12]

#### **Chapter 13**

## Genomic Surveillance and Intervention on Dengue Virus in an Urban Setting in the Philippines

*Francisco M. Heralde III, Glenda B. Obra and Maria Perlita B. Apelado*

#### **Abstract**

This is part of the ReMoVE Dengue Program (i.e., research on mosquito, virus, and eco-socioeconomics of dengue) initiated under the auspices of the National Research Council of the Philippines, which started in 2012 aimed to develop locally adapted technologies, products, and systems, which would control the spread of dengue virus and reduce the eco-socioeconomic impact of dengue. Here, will be reported the results of the genomic surveillance of community-collected mosquitoes from a dengue hotspot community of Barangay Old Balara in Quezon City, Philippines using serotype-specific dengue PCR, and the developed antisense RNA product platform for dengue virus control based on surveillance results. Implications and recommendations for this work are outlined.

**Keywords:** genomic surveillance, dengue PCR, dengue hotspot, antisense RNA, virus control, surveillance-based intervention

#### **1. Introduction**

Dengue remains to be a major problem in several Metro Manila cities and in the entire country. Since 2011, dengue cases in the Philippines continue to rise at an average rate of 3900 cases per year, with recorded cases of 34,940 in 2022 [1]. Among the regions, Central Luzon is with 6641 or 13%; Central Visayas, 6361 or 12%; and Zamboanga Peninsula, 4767 or 9% were the top contributors [2]. The increasing cases reflect a number of underlying scenarios and causes, which are difficult to pinpoint, although, one thing is clear, the current strategies for control and mitigation may not be as successful in containing the growing problem of dengue. The Philippines has stood as first in dengue cases globally, like the first recorded dengue epidemic in Southeast Asia that occurred in Manila in 1954, and the highest dengue case contribution ever recorded globally in 2019 of 437,563 cases [3]. It is amazing that despite government efforts and programs, this mosquito-borne disease continues to successfully become endemic and ravage the population [4]. Perhaps, a series of unfortunate events contributed to this unsuccessful mitigation, like the "lack of empowerment among the stakeholders in taking responsibility for dengue prevention" despite the

Philippine government's established National Dengue Prevention and Control Program in 1993 as well as the failed Dengvaxia vaccine program launched in 2016 [3], although other reasons may underlie this scenario. Nevertheless, optimistic perspectives remain as new research shed light on better strategies for control and mitigation [5]. Among these strategies, the dynamics of the virus-vector interaction and the phenomenon-based targeting may hold the key to dengue's long-term prevention and control (**Figure 1**).

*Aedes aegypti* is the primary vector of the dengue virus, although *Aedes albopictus* has also been identified as a minor vector [6, 7]. Apparently, as more urban communities expand (i.e., which is a common trend among cities with increasing population) to cover semi-urban, semi-rural, and forested areas, the *Aedes* mosquitos have adapted to survive and breed in water pools and deposit in these areas. The Philippine Department of Science and Technology's Ovicidal and Larvicidal (DOST's-OL) trap technology was adopted in 2011 as a widespread strategy for controlling mosquitos [8]. The OL-trap technology involved the use of agents that can kill mosquito eggs and larvae in stagnant freshwater containers that serve as traps. Meanwhile, another kind of trap, the Orbi-traps has been validated as means to monitor mosquitos in different localities [9]. In particular, the Orbi-trap procedure has been utilized in monitoring A. *aegypti* mosquitoes and correlated with dengue cases in Manila [9]. Following a simple mosquito trap design [10] with modifications, adult mosquitos may be caught and

#### **Figure 1.**

*The conceptual framework for genomic-based surveillance and intervention. A. Dengue as a threat to all with breaches in vector control and host protection. B. Genomic surveillance and intervention as a cornerstone in the fight to control dengue.*

*Genomic Surveillance and Intervention on Dengue Virus in an Urban Setting… DOI: http://dx.doi.org/10.5772/intechopen.109631*

morphologically identified. Further propagation of this scheme through a DOST invention [11] could be augmented by monitoring the virus present in the collected mosquito through a PCR analysis, thus may give early advice on the type of dengue virus circulating among the mosquito population in the community.

The PCR platforms for dengue virus detection are widely available in various institutions, the academe among others, and may be utilized for community-based surveillance, especially when appropriate community-academic institution link-up is established, especially now with several molecular laboratories with PCR machines being underutilized as COVID-19 testing declines [12–14]. Furthermore, what is needed would be a system for sample collection, the reagents for the genomic surveillance work, and an online-based reporting system accessible to the community, a model considered and espoused in this project [15]. PCR protocols for routine MDRTB, H1N1 virus, and leptospirosis detection have been established in the Department of Biochemistry and Molecular Biology—University of the Philippines College of Medicine (DBMB-UPCM). The laboratory had an extensive experience with MIRU-VNTR analysis and sequence analysis, including the use of appropriate bioinformatic software. Application of similar strategies to the dengue virus would be convenient.

Genomic-based interventions could be installed in the Orbi-traps, such as a mosquito-feeding device, where anti-dengue interventions can be incorporated into the blood formula. Several studies have demonstrated the positive response of mosquitoes in feeding warm blood [16–19]. The feeding device, however needs to be designed, although "blood-filled condoms" have been reported to work in luring mosquitos [19, 20]. Anti-dengue DNA vaccines have also been reported to elicit an immune response in humans [21]. Meanwhile, mosquitos can be ideal vaccine targets, capitalizing on their endogenous defense system to block the spread of the dengue virus [22].

A set-up where a suitable container, such as a condom, with a chemical-based heating system [20] and incorporated with lactic acid and carbon dioxide would be ideal to attract mosquitos to the feeding device and insure consumption of an antidengue vaccine. The DBMB-UPCM has reasonable experience in recombinant DNA work, including the design and production of plasmids for various uses, including sequencing, expression, and DNA vaccines. Some constructs reported in the literature can be tested in the process.

DNA vaccines have been demonstrated in the control of West Nile virus *via* vaccination of American robins—the intermediate host involved in viral amplification that is feeding on *Culex* mosquitos [23]. Meanwhile, the mosquito defenses against the dengue virus have been studied to involve the JAK–STAT pathway, where a specific RNAi-based inhibition of PAIS or protein inhibitor of activated STAT results in increased survival of mosquitos from bacterial or viral challenge [24]. Similarly, an oral administration of DNA nanoparticles synthesized by complexing plasmid DNA with chitosan, a natural biocompatible polysaccharide, was shown to result in transduced gene expression in the intestinal epithelium [25]. Furthermore, the *Wolbachia* wMelPop strain, an endosymbiotic bacterial pathogen was found to be transferrable from *D. melanogaster* to the mosquito *A. albopictus* with the consequential effect of reduced longevity and fecundity, and high embryonic mortality [26]. While in *A. aegypti*, increased locomotor activity and metabolism were reported [27]. Thus, a protocol involving orally delivered DNA construct that would modulate the mosquito immune response combined with bacterial coinfection would manage dengue viral and bacterial residency in the vector, thus presenting an avenue for combined

antiviral and bacteria-based control. This concept was applied in a study, where a cationic liposome was utilized to deliver an expression construct with the gene for *Ae. aegypti* thioester-containing proteins (AeTEPs), (i.e., involved in the control of flavivirus infection), resulting in reduced dengue virus infection [22].

This project was proposed to add value to a program of wide-scale mosquito monitoring by surveillance of the virus present in the collected mosquito by PCR analysis of its DNA/RNA extract and provide advice on which dengue type is circulating in the mosquito population of a given site. Furthermore, in the Orbi-trap, a mosquito-feeding device could be installed, where an anti-dengue DNA vaccine could be introduced.

#### **Figure 2.**

*Mosquito collection summary and dengue PCR test results of the three sampling sites A. Luzon, B. Old Balara, and C. Sitio Payong in year 1. The red highlights indicate the households are positive for dengue, and the yellow is negative for dengue. Entries with zero values and yet show red highlights indicate the late emergence of mosquitoes from the collected sample, which comes from the eggs. Note the increasing number of houses with positive for dengue more than 3–4 houses, starting from the sixth to the eighth collection. There were houses that consistently show dengue positive mosquitos. Mosquito counts of the three sampling sites: D. Luzon, E. Old Balara, and F. Sitio Payong. Most of the houses yielded in their vicinity (outside) a count of 0–50 mosquito individuals (i.e., larvae, pupa, and adult), a moderate number of houses with 50–100 counts, and a few houses with 100–150 counts across the different collection times. In terms of counts greater than 150, Old Balara had more instances across the different collection times followed by Sitio Payong and lastly by Luzon. G. Project experimental site in Quezon City, Philippines [28].*

*Genomic Surveillance and Intervention on Dengue Virus in an Urban Setting… DOI: http://dx.doi.org/10.5772/intechopen.109631*

In the first year of the project, a study to evaluate a holistic vector control program was embarked, which involved strategies, such as genomic surveillance and intervention, herbal-based larval destruction, irradiation-induced sterility of mosquito, and biocontrol-organism based larval control among others (ReMoVE Dengue Program research on mosquito, virus, and eco-socioeconomics of dengue). Mosquito traps were installed in three sites in Barangay Old Balara, Quezon City, at 15 houses per site and 6 traps (i.e., 3 inside and 3 outside) per household, with GPS coordinates determined. The captured mosquitos were counted bi-weekly from May 2012 to January 2013 and serotype-specific dengue PCR was used for monitoring viral presence. In years 2 and 3, monitoring work was continued in the three sentinel sites (i.e., three houses per sentinel site). Also started the development of anti-dengue dsRNA as well as the validation of trans-ovarian dengue transmission and virulence testing in a mouse model. This report outlined the findings of this community-based study.

#### **2. Materials and methods**

#### **2.1 Sampling and nucleic acid extraction**

The experimental site has been identified and mosquito traps have been set up in a total of 45 houses (15 houses per site with 3 traps indoors and 3 traps outdoors). The sites were Area 1- Luzon, Area 1- Old Balara, and Area 4- Sitio Payong, with prior consultation and approval of the Quezon City Health Department (**Figure 2G**). Two Orbi-traps per site and six OL-traps per household (3 indoors and 3 outdoors) were installed.

The Barangay Health Workers (BHW) together with the project science research assistant conducted the biweekly sample collection. The Orbi-traps were utilized to monitor the adult mosquitos, while the OL-traps were utilized to monitor the egg and larval stages. The collected samples were sent to the DBMB-UPCM, where all field samples were stored, counted, identified, and processed, for RNA extraction and dengue detection by PCR. A small area (i.e., a mosquito insectarium, **Figure 3B**) has been set up for growing larvae collected from the field prior to molecular analysis. Preserved samples per collection receptacle (Orbi-trap or OL-trap at 1–50 mosquitoes and in cases exceeding 50, random sampling was done) were pooled and processed for RNA extraction using Qiagen RNEasy Kit following the manufacturer's protocol.

Reagents, materials, and samples were procured for the project, including an electronic air temperature and wind velocity meter, mosquito traps, primers, and laboratory and office supplies.

#### **2.2 Detection of dengue virus by reverse-transcriptase-PCR**

#### *2.2.1 First strand synthesis*

Following the protocol of Lanciotti et al. [29], target viral RNA was converted to a DNA copy (cDNA) using reverse transcriptase (RT) and the dengue virus downstream consensus primer (D2). The first strand synthesis was done using the Omniscript or Promega (Qiagen, Macare Philippines, Golden Bat (Far East) Inc., respectively) following the manufacturer's protocol.

#### **Figure 3.**

*Antisense RNA trial testing on mosquitoes in the community. A. Preparation of antisense RNA formula with honey solution. B. Simulated mosquito setup in the community for the trial testing, collection of specimens from ovi-traps, and the insectarium used in the lab for handling and hatching the specimens. C. Electropherogram of dengue-PCR results of antisense RNA fed vs. non-fed specimens. Representing TS1-serotype 1,TS2-serotype 2,TS3- serotype 3, and TS4-serotype 4 conducted in different locations, Area 1—Old Balara and Area 4—Sitio Payong. Notable is the specific disintegration of signals in fed vs. non-fed and brown sugar only. D. Dengue-PCR of larva specimens from fed samples with the persistence of serotypes 2 and 4.*

#### *2.2.2 Polymerase chain reaction*

Serotype-specific amplification was done from the cDNA template with the upstream dengue virus consensus primer (D1) and the downstream serotype-specific primers (i.e., TS1, TS2, TS3, and TS4). Target cDNA was amplified in 10-μl volumes

*Genomic Surveillance and Intervention on Dengue Virus in an Urban Setting… DOI: http://dx.doi.org/10.5772/intechopen.109631*

containing the following components: 10 mM Tris (pH 8.5), 1.5 mM MgCl2, 10 uM each of the four deoxynucleotide triphosphates, 10 pmol each of primers 1 (D2) and 2 (i.e., either of TS1, TS2, TS3, and TS4) and 0.5 U of TopTaq (Qiagen, Macare Philippines) or GoTaq (Promega). The PCR reaction profile consists of the following: initial denaturation (94°C, 1 minute), and then to proceed with 35 cycles of denaturation (94°C, 30 s), primer annealing (55°C, 1 min), primer extension (72°C, 2 min), and followed by a final extension step of 72°C for 10 min.

#### *2.2.3 Agarose gel electrophoresis*

The PCR products were analyzed by gel electrophoresis on a 2.5% agarose gel (Vivantis) containing Gel Red (0.5 ug/ml), with the settings of 75 volts, for 40– 45 minutes. A band on the agarose gel of the correct size was interpreted as a positive result. A faint band of the correct size was considered an equivocal result.

#### **2.3 Anti-dengue dsRNA study**

Primers targeting conserved regions in the UTR-Core gene were designed. The primers are:

UTR36 5<sup>0</sup> -GCTTAACGTAGT(T/G)CTAACAGTTT-3<sup>0</sup> 62 deg CAP521rc 5<sup>0</sup> -AACATGTGCACCCTTATAGCGA-3<sup>0</sup> 64 deg T7UTR36 5<sup>0</sup> -GAAATTAATACGACTCACTATAGGGGCTTAACGTAGTKC-TAACAGTTT-3<sup>0</sup>

T7CAP521 5<sup>0</sup> -GAAATTAATACGACTCACTATAGGGTCGCTATAAGGGTG-CACWTGTT-3<sup>0</sup>

The translation product of the target region is shown in **Figure 4** panel A, and the region targeted in the viral genome is shown in panel B. The primers are used in the subsequent cDNA and dsRNA synthesis of RNA extracted from female *A. aegypti* mosquitos infected with DENV obtained from Barangay Old Balara, Quezon City. The

**Figure 4.**

*A region in dengue viral genome targeted for dsRNA.*

synthesized dsRNA is administered to a group of mosquitos alongside a parallel treatment of control RNA with mosquitos coming from the same population. The presence of the dengue virus serotypes, after 2 days posttreatment, is detected through nested PCR.

#### **3. Results**

#### **3.1 Sampling and nucleic acid extraction**

In the initial year of community genomic surveillance, 12 sampling events were conducted. Mosquitos from the first to the twelfth sampling were tested for dengue-PCR using standard protocols as described. An increasing trend of more than 3–4 houses per site was found positive for dengue (Panel A–C, **Figure 2**). Twelve sampling data points for Area 2- Luzon, Area 1- Old Balara, and Area 4- Sitio Payong were uploaded to the project website [15]. The goal was to provide online access to the Barangay Health workers and use the information in their search and destroy program for the breeding ground of the mosquitos. This way, their campaign will be focused on the critical spot in the community. The other objective also was to guide the community as to which areas to avoid as possible exposure sites for the dengue-infected mosquitos.

The mosquito counts from the first to the twelfth collection were plotted as shown in **Figure 2** (Panel D–E). It can be noted that variable counts were obtained for each household. Most of the houses yielded mosquitos in their vicinity (outside) with counts of 0–50 mosquito individuals (i.e., larvae, pupa, and adult). A moderate number of houses yielded counts of 50–100 mosquito individuals and a few houses with 100–150 counts across the different collection times. There were collection times where these counts were exceeded; and in Area 1- Old Balara, in particular, there were two instances, where it had counts exceeding 150 specimens per collection, followed by Area 4- Sitio Payong and lastly by Area 2- Luzon. This result was correlated with the cleanup program of the community and the prevalence of dengue cases.

Mosquito samples were submitted to the Research Institute for Tropical Medicine (RITM), Dept of Medical Entomology, for taxonomic identification. The results showed a 100% match for the preliminary identification in the lab and those identified in RITM, where most of the samples are *A. aegypti* and a few are *A. albopictus* and *Culex sp.* (See **Figure A1**).

A coordination meeting with RITM was conducted toward organizing a dengue study group. The RITM Virology Lab shared a protocol to detect dengue by RT-PCR. This procedure was optimized to detect the dengue virus in mosquitoes and was used in the analysis of the specimens collected from the different communities, including those submitted by the Philippine Nuclear Research Institute (PNRI, which were reared in the PNRI Mosquito laboratory for several generations) (**Figure 5**). Rearing of *Ae. aegypti* larvae were done using deionized water and commercial fish meal (Tetramin, Tetra GmbH) at 0.02 mg/larva/day. Pupae are collected as soon as they develop. Adults were confined in a rearing cage (1 ft3 ) and fed with a 10% sugar solution. Adult females were blood-fed using immobilized live mice. Egg collection was done using an egging cup (40 mL cap.), containing about 10 mL deionized water and lined with white filter paper for oviposition. *Ae. aegypti* was reared in laboratory conditions with a mean temperature of 27°C, relative humidity of 70%, and photoperiod of 12:12 (light: dark).

*Genomic Surveillance and Intervention on Dengue Virus in an Urban Setting… DOI: http://dx.doi.org/10.5772/intechopen.109631*

#### **Figure 5.**

*Results of selected mosquito samples analyzed for the 4 serotypes. Lanes 21 and 31 indicate the presence of serotype 2 and 3 in the same male* Aedes *sample and only serotype 2 (lane 22) for the female sample. Note the multiple bands, indicating multiple genotypes for each serotype.*

Initial results indicated that 8 out of 10 specimens are dengue positive, with both male and female mosquitos showing positive results for the dengue virus infection. These infections could be vertically transmitted (maternal to offspring) as the samples were obtained from hatched larvae that were reared to the adult stage (**Figure 6**). The same pattern was observed in the samples collected from the traps set up in Barangay Old Balara where larvae were made to hatch, and the emerging adult mosquitos were analyzed for the presence of the dengue virus. Results showed that multiple dengue serotypes could infect one mosquito and multiple genotypes within a serotype can also occur (**Figure 5**). Vertical transmission has been reported to occur among dengue viruses in the *Aedes* mosquito [30–32]. The findings of this study are consistent with these previous reports.

In the second year of genomic surveillance in the community, eleven sampling events were established and monitored. The mosquito collection from the first to the eleventh collection was processed, recorded, and summarized as shown in **Figure 7**. It was seen from the trend that there was a persistent prevalence of mosquitos in Area 2 followed by Area 4 and least by Area 1. As expected, most collections were larvae and pupae with most samples coming from Area 2, followed by Area 4, and lastly by Area 1 (**Figure 6**).

Areas 1 and 4 are more forested communities as compared to Area 2, which contrasts with the expected pattern that *A. aegypti* tends to prefer forested areas. The low trapping yield in Area 1 could also reflect on the anti-dengue mosquito program of the community as the community health center is located in Area 1.

It can also be noted that the pattern where the majority of the strongly denguepositive mosquitos were those collected in the second to the sixth collection, which were from August to November and began to decline in the seventh to the eleventh collection, which was from December to February. Most of the strongly denguepositive specimens were found in Areas 2 and 4. These findings on the dengue PCR

#### **Figure 6.**

*Distribution summary of mosquitoes collected from the three sentinel sites in Bgy Old Balara. Area 1 (Old Balara), Area 2 (Luzon), and Area 4 (Sitio Payong) in year 2. Firstto eleventhcollection (A). Table 5-1 summarize the counts of specimens collected (B). Dengue-PCR results of the specimens collected and scoring best on the degree of dengue positivity (C-D) with red meaning strongly positive and yellow as weakly positive.*

pattern tend to support the collection data in **Figure 6**. This means that vector surveillance with accompanying RT-PCR detection of the dengue virus serotypes can provide an additional layer of information that would reflect the seasonal variations of dengue infestation of the mosquito vector as well as the dengue management program of the community.

#### **3.2 Development of antisense RNA for dengue virus in mosquito**

The RNAi protocol developed was implemented, and was able to yield antisense RNA products for testing on mosquitos. Two trials were conducted on RNAi-based inhibition of the dengue virus in the *Aedes* mosquito derived from Barangay. Old Balara is shown in **Figure 7**. Evaluation of a mosquito feeding device for RNAi construct delivery system was not pursued as direct brown sugar feeding was found to be a simple strategy considering that RNA is stable in a sugar solution. Apparently, the simpler the delivery system is, the better it will be for community-based intervention. In the result shown in **Figure 7**, we can see that the feeding of antisense RNA in 4– 7 days resulted in the shearing of dengue viral RNA. The mosquitos mostly die on the fourth day, indicating the lethality of the antisense RNA. It was also observed that those mosquitos that survived on the 7th day showed clearance from all serotypes.

The test was repeated to evaluate which of the following antisense RNAs will best work: dsRNA non-hybridized, dsRNA hybridized, ssRNA+ strand, or ssRNA-strand. The results of this experiment are shown in **Figures 7** and **3**. Only the dsRNA hybridized *Genomic Surveillance and Intervention on Dengue Virus in an Urban Setting… DOI: http://dx.doi.org/10.5772/intechopen.109631*

#### **Figure 7.**

*Antisense RNA synthesis and trial testing on mosquitoes. A. Preliminary antisense RNA synthesis results. B. Results on antisense RNA representing 4 days and 7 days feeding with RNAi. TS1-TS4 represents the four dengue serotypes. Notable is the disintegration of signals in 4 days (i.e., shearing of DNA) as compared to brown sugar and 7 days (i.e., faint shearing of DNA). The antisense produced also affords protection of different serotypes. C. Trial 3 results in antisense RNA representing 4 days feeding with RNAi and comparison of different RNAi types. Notable is the specific disintegration of signals in TS2 but not TS1 as compared to brown sugar only. The lowest bands are primer dimers.*

showed activity in the specific inhibition of TS2. There is an endogenous reduction in TS2 dengue signal with sugar alone, while intensification of signal with either ssRNA+ strand or ssRNA-strand was observed. In this sample, no serotype 3 or 4 was present. It can be noted that TS1 is not inhibited when the designed RNAi is generic.

#### **3.3 Vertical transmission of dengue in in-house propagated mosquito stocks**

Specimens from F1 to F15 generation obtained from the PNRI were analyzed with dengue PCR results shown in **Figure 8**. It can be observed that a persistent occurrence



#### **Figure 8.**

*Summary dengue PCR results of F1 to F15 generation of mosquito samples in-house bred in PNRI. Dengue-free eggs emerged in F10 as shown in green. Dengue-positive mosquitoes are shown in yellow (i.e., weakly positive) and red (i.e., strongly positive).*

of the dengue virus from F1 to F10 samples (variable pattern could arise from a random sampling of 3 M/F/E samples). We observed the presence of different serotypes in one mosquito in females, males, and egg samples. We also observed the presence of different genotypes in one serotype (multiple bands were verified by sequencing, which will be reported in another paper). A yield of dengue-free eggs was observed in F10. Thus, the transovarial transmission of the dengue virus in local *A. aegypti* mosquitos has been verified. We also analyzed a batch sample of mosquito eggs consisting of 20 eggs. The dengue PCR results show only four eggs positive with serotype 1 and none for all the other serotypes (See **Figure A2**). This shows that the infection rate for vertically transmitted dengue virus template from parent to egg is approximately 20%.

*Genomic Surveillance and Intervention on Dengue Virus in an Urban Setting… DOI: http://dx.doi.org/10.5772/intechopen.109631*

Whether the amplicons detected through this dengue-specific PCR represent authentically, and live viruses may require definitive proof by DNA sequencing. Such will be presented in another paper.

A study on transovarial transmission of dengue in correlation with virulence in mice was conducted by our graduate student (i.e., Mr. Ralph Bawalan—MS Trop Med) in collaboration with Dr. Nelia Salazar—RITM Entomologist. A mouse model for dengue testing was developed. This model was able to show histological similarities with humans as well as pathological symptoms of thrombocytopenia and fever (See **Figure A3**).

#### **3.4 Genomic surveillance in year 3 and strategy for mitigation**

The genomic surveillance was continued for Area 1-Old Balara, Area 2-Luzon, and Area 4-Sitio Payong through their sentinel sites. The mosquito/larvae/pupae collected from the sites from first to the nineth collection and their respective dengue PCR results are summarized as shown in **Figure 9**. It can be observed that at all sites, there




#### **Figure 9.**

*Distribution summary of the genomic surveillance in year 3. A. Table 8-1 contains the consolidated mosquito specimens collected from the different sites. B. Dengue PCR amplicon electropherograms of community specimens. C. Dengue-PCR results of the specimens collected and scoring based on the degree of dengue positivity with red meaning strongly positive.*

was a strong positivity for the dengue virus, indicating a worsening dengue infection from the community mosquito population after 3 years of surveillance. Apparently, the 4S strategy of the community does not seem to work sustainably in containing the spread of the virus. How this correlates with the dengue disease burden of the community may have to be closely evaluated.

The remaining mosquito larvae' homogenates and extracts were evaluated for their potential use as templates for the antisense experiments. The plan was to amplify the dengue virions that can be recovered from intra-cranial injections in suckling mice, a procedure that was previously optimized by our team (i.e., based on **Figure A3**).

A community trial of the antisense RNA formulation was installed in Area 1 (Old Balara) and Area 4 (Sitio Payong). The fourth and sixth batches of collected samples that are positive for dengue virus (serotypes 1 to 4) were utilized in the experiment (**Figure 3**).

After 2 weeks of exposure, specimens were collected, extracted, and tested for dengue-PCR. The results showed low to the absence of signals in antisense RNAi-fed.

specimens as compared to those that were not fed. The results are consistent with the previous findings. Even in the community environment, the antisense RNA preparation was able to inhibit the dengue virus transmission in the mosquito (**Figure 3**). It was also noted that in an ovi-larvae trap model, there was inhibition of the dengue virus, which is carried over to the emerging mosquito. This is a new indication of the developed antisense RNA.

#### **4. Discussion**

Since 2012, three studies have been conducted in the Philippines that verified and validated the natural vertical transmission of the dengue virus in a community population [12–14]. Similarly, there were seasonal variations in dengue positivity in the mosquito, mostly occurring in the rainy seasons of August to November, which is aggravated by possibilities of multiple serotypes and multiple genotype patterns, indicating that the next generation of eggs laid by a dengue-infected mosquito become the melting pot for possible dengue virus recombination. Apparently, the data also indicate that the *A. aegypti* mosquito has been successfully adapting, breeding, and successfully thriving as a coexisting dengue vector in urban communities and the absence of forested areas no longer limits its geographical spread. Through the years, while the *Aedes* mosquito has continued to infiltrate the urban communities, the mitigation strategy implemented by the Department of Health to all the Barangay communities has not taken major leaps and still follows the 4S Program (DOH website). Thus, updated and leveled-up interventions may have to be implemented and integrated into community-based strategies to be able to see concrete progress in dengue intervention. As outlined in the conceptual framework in **Figure 1B**, the genomic surveillance strategy for the dengue virus harbored by the natural stocks of mosquitos captured from ovi-traps in sentinel sites in the community may have to be set up in coordination with the barangay health center and neighboring academic or coordinating research institutions with existing PCR facilities for routine molecular detection followed by online reporting of results to allow quick action of the community to implement various interventions. Furthermore, given the knowledge of the circulating dengue serotypes and genotypes in the mosquito community population and their potential to persist in the next generation of mosquitos, various genomicbased interventions may be designed and implemented, among them are the sterile

*Genomic Surveillance and Intervention on Dengue Virus in an Urban Setting… DOI: http://dx.doi.org/10.5772/intechopen.109631*

insect technique, which introduces noninfected, sterile male mosquitos that will breed in natural stocks and control the egg-laying potential, thus gradually controlling the natural mosquito population. The other approach is through this *Wolbachia sp*. infection, a natural bacterium selectively growing in *Aedes* mosquitoes and would result in the eventual death of the infected mosquitos, thereby reducing the natural population. Another approach, which is done in this study is by antisense RNA, which can be designed based on the circulating variant of the virus, the templates of which are derived from the genomic surveillance DNA/RNA extracts, and are introduced or actively fed to mosquitos in the communities to block the vertical transmission of the circulating dengue viruses. Since it is not entirely possible to eliminate the mosquito population, the antisense RNA can be designed to not only block the dengue vertical transmission but also provide gene-targeting strategies that would reduce reproductive capacities, including among others egg-laying or hatching potentials. The feeding platform may involve simple technologies readily adaptable to communities such as the brown sugar solution used for feeding insects, such as butterflies, which may be enhanced with lactic acid or blood meal to promote mosquito consumption of the antisense RNA formula. The challenge; however, in this approach is assessing the long-term safety and efficacy of double-stranded RNAs and their effect in reshaping the patterns and demographic structure of the dengue virus in the natural mosquito population. The health benefits to humans though may outweigh the ecological impact of this type of mitigation.

#### **5. Conclusions and recommendations**

The genomic surveillance from year 1 of the three areas in Barangay Old Balara, an urbanized area showed an increasing trend of more than 3–4 houses per site (20–27%) that are found to be positive for dengue. A website established to report results of the genomic surveillance found utility for the online access of the Barangay health workers and provided support for their search and destroy program against the breeding ground of mosquitos. Species identification of the community-collected specimens indicated the majority to be *A. aegypti* and a few *A. albopictus* and *Culex sp*. The RT-PCR surveillance revealed the presence of multiple dengue serotypes in one mosquito specimen and multiple genotypes within a serotype. There was a persistent prevalence of mosquitos in Area 2 followed by Areas 4 and 1, considering that Area 2 was less forested, which contrasts with the expected pattern for *A. aegypti,* which tends to prefer forested areas. The low trapping yield in Area 1 reflects the antidengue mosquito program of the community as the community health center is in Area 1. Strong dengue positivity was found in mosquitos collected in the second to the sixth collection, which was from August to November and declined on the seventh to the eleventh collection, which was from December to February. This indicates that the vector surveillance with accompanying RT-PCR detection of the dengue virus serotypes can provide an additional layer of information that would reflect the seasonal variations of dengue infestation of the mosquito vector as well as the possible congruence of the dengue management program of the community.

The antisense RNA preparation that was developed based on the dengue amplicons obtained from the genomic surveillance was able to inhibit the dengue virus transmission in the mosquito from one generation to the other in a simulated community setting. Further studies can be done to evaluate the potential utility of a genomic surveillance-based antisense RNA platform in real-life community scenarios. While

vertical transmission of dengue has been established as a known mechanism for the persistent presence of dengue in *Aedes* mosquito populations found in the communities, the current 4S strategy implemented locally may not be adequate to control the rising dengue cases and an active genomic-based intervention to block this vertical transmission must be done.

#### **Acknowledgements**

Special thanks to the National Research Council of the Philippines (NRCP) for the research grant of FMH (NRCP Grant # N-001). Also, thanks to the assistance and support of the Quezon City Health Department, particularly Dr. Antonieta Inumerable and Dr. Rolly Cruz; and the officials of Barangay Old Balara, Quezon City, particularly Hon. Beda Torrecampo and Dra. Karen Alcid-See. Special thanks to Dr. Cecilia Reyes, Entomologist and former Director of NRCP who engaged our team in this project, Dr., Lourdes J. Cruz, National Scientist and former President of NRCP, all the NRCP management and staff who help us through the years, especially Ms. Renia Corocoto and Mr. Caezar Arceo, and the other members of the ReM0VE Dengue Program, Dr. Grace Yu, Dr. Nelia Salazar, Dr. Judylin Solidum, Dr., Pio Javier, and Dr. Erlinda Torres.

Special thanks also to Ralph Bawalan, former MS Trop Medicine student who worked with us and now pursuing his Ph.D., and his adviser, Dr. Nelia Salazar.

#### **Conflict of interest**

The authors declare no conflict of interest.

*Genomic Surveillance and Intervention on Dengue Virus in an Urban Setting… DOI: http://dx.doi.org/10.5772/intechopen.109631*

#### **Appendix**


#### **Figure A1.**

*Entomological report certifying the taxonomic identity of the collected mosquito from the community.*

**Figure A2.**

*Electropherogram of the PCR products of 20 mosquito eggs from F10 generation showing approximately 20% infection rate.*

*Genomic Surveillance and Intervention on Dengue Virus in an Urban Setting… DOI: http://dx.doi.org/10.5772/intechopen.109631*


#### **Figure A3.**

*Viral expansion through neonate intra-cranial injection of RNA extracts from community-collected mosquito specimens and virulence assay in mice of the subsequent generation.*

#### **Author details**

Francisco M. Heralde III<sup>1</sup> \*, Glenda B. Obra2 and Maria Perlita B. Apelado<sup>3</sup>

1 Department of Biochemistry and Molecular Biology College of Medicine, University of the Philippines, Manila, Philippines

2 Department of Science and Technology-Philippine Nuclear Research Institute, Quezon City, Philippines

3 Molecular Diagnostics and Cellular Therapeutics Laboratory-Lung Center of The Philippines, Quezon City, Philippines

\*Address all correspondence to: fmheralde1@up.edu.ph

© 2023 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

*Genomic Surveillance and Intervention on Dengue Virus in an Urban Setting… DOI: http://dx.doi.org/10.5772/intechopen.109631*

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## Dengue Reduction through Vector Control

*Eduardo A. Fernandez Cerna, Catalina Sherman and Mercedes Marlene Martinez*

#### **Abstract**

Dengue fever is a disease transmitted by the mosquito *aegypti*. There is a secondary vector: Aedes albopictus with some epidemiological importance in the transmission of dengue. Pharmacological treatment for dengue is a palliative treatment for the disease and there is an absence of a universally accepted vaccine for the different clinical infections. In these circumstances, the interruption of the infection cycle is possible basically through the reduction of the *Aedes aegypti*, reducing its breeding sites or physically reducing its population through chemical or biological means. Traditional approaches to vector control are becoming less effective as a result of the combination of resistance to insecticides and the logistic complexity of covering increasingly large urban centers with the same number of health workers as in past decades. Experiences in different countries reflect the need to involve more actively families and communities in the reduction of breeding sites. Several innovations have been introduced using biological methods, physical control of sources, and involvement of families and schools in vector control. The possibility to scale up successful experiences requires a joint effort of governments and communities to tackle mosquito source reduction and add a multipurpose concept of domestic hygiene.

**Keywords:** dengue, *Aedes aegypti*, breeding sites, control methods, community, hygiene

#### **1. Introduction**

Dengue fever is a viral infection transmitted by a mosquito. Different studies calculate that 3900 million people are living at risk of contracting a dengue infection. According to model-based estimations every year, there are 390 million infections caused by the dengue virus, and from those 96 million present clinical manifestations ranging from very mild to extremely severe and life threatening [1].

Dengue fever is endemic of tropical and subtropical regions where weather conditions favor the presence of its vector *A. aegypti* mosquitoes and its alternative vector *Aedes albopictus* with more prevalence in Asia but is now also present in the Americas. In these regions, the contrasting conditions of rainfall and severe lack of accessible water supply enable the presence of breeding sites in artificial containers filled by the rainfall during the rainy season and water reservoirs kept by the population to assure its access during the severe dry season (tropical summer) [2, 3]. Interestingly enough, natural conditions and human behaviors induced by the need to have access to reliable water supply are the catalyzers to the presence of high densities of *A. aegypti* mosquitoes and as a consequence the transmission of dengue fever [4], which is explained in its clinical characteristic elsewhere in this book.

Dengue is caused by a family of viruses (flavivirus) that are carried by the *A. aegypti* females from infected human hosts to healthy but susceptible human hosts (ready to be infected) that establish a cycle of human-mosquito-human that repeats constantly keeping the viral activity and its transmission in the population [2, 3].

The transmission cycle cannot be interrupted by curative drugs (to reduce the number of cases of dengue infection), prevention through vaccines has been tried but after unsuccessful attempts to introduce effective vaccines, the pharmaceutical industry continues to work in safe vaccines without definite results [5].

The only alternative currently, as was the case a century ago, is to interrupt the transmission by reducing the population of *A. aegypti* through the elimination of the adults and immature forms (eggs, larvae, and pupae) or by making an effort to reduce the breeding sites through improving sanitation measures in human dwellings and peridomestic areas. In the 1920s, there was an extraordinary effort to eliminate the vector *A. aegypti* completely based on the destruction of breeding sites, the results were impressive in the areas it occurs under the leadership of Dr. Fred Sopper, but it was not complete and now, the objective is the reduction of Aedes populations rather than complete eradication [6].

In the Public Health field, there is a current tendency to integrate the different programs in more comprehensive approaches where local health actions are useful to get more objectives completed in large thematic areas such as environmental health improving the access to water, optimizing the refuse systems, and the beautification of peridomestic areas in the different neighborhoods.

Vector control in the twenty-first century requires not only a clear government commitment to this activity but a convinced and active population participating in the different required tasks.

This chapter then discusses strategies for population reduction through vector control.

#### **2. Type of** *A. aegypti* **breeding sites**

*A. aegypti* is the primary vector for dengue fever as well as responsible for the transmission of other diseases such as yellow fever, zika, and chikungunya that have produced epidemics throughout recent history. And most of this chapter will discuss about its control [1, 7].

The *A. aegypti* mosquito in its life cycle goes through immature stages to mature or adult stages (**Figure 1**).

The female mosquito is responsible for the transmission of dengue since in her need to obtain human protein to form eggs bites human hosts and feeds in their blood and at the same time inoculates the dengue virus. Once the female is fed is ready to complete the egg formation and lay in deposits with water where it can remain viable for days to months, once the egg hatches it becomes larvae for 4–5 days before evolving into pupae, and this stage is previous to the adult one that is reached in two days.

The immature stages then include eggs, larvae (instar I through 4), and pupae that are aquatics. The immature stages require deposits with water where these stages can be complete—those deposits are called breeding sites.

#### **Figure 1.**

Historically, breeding sites for *A. aegypti* have been classified as: discardable and water storage containers. The discardable are usually those that are kept or thrown in peridomestic areas of the household and usually do not have an economic or utilitarian value and are the product of deficiencies in the refuse systems and/or behaviors to retain articles assuming a future use.

Discardable containers become more important during the rainy season because of their abundance in the patio; the propensity to fill with small volumes of rain and the possibility to collect water during consecutive days of rainfall. Their role as breeding sites is completed during periods of rain remissions when the female mosquitoes can lay eggs and those already in the deposits can hatch and produce the larvae forms [8, 9].

The water storage containers exist in the patios as a result of deficiencies in the regular supply of water to the households and the resulting behavior of the families to keep water collected from rain, water stream, or the water supply service when there is a chance to obtain it [9, 10]. It is worthy to mention that some discardable containers are kept in the patios with the expectation to assign a function in the future. Used tires are an example of containers with potential subjective use [11].

A third category of containers is the natural reservoirs like the leaves of some ornamental plants (bromeliads), or tree holes in the patios [8].

#### **3. Control methods**

Traditional control has been based on two strategies: reducing discardable containers and using larvicides in those water storage containers. These approaches target the vector in its immature and/or adults' stages. These methods have to do with the use of chemical products: larvicides when directed to larvae or adulticides when the mature stages are targeted.

In the last twenty years, formulations with chlorine by itself or in combination with detergents have been used in different countries in America [12, 13]. In Honduras, there were assays with sodium chlorine (kitchen salt) and limestone to modify the environment of containers like tires to make unlikely the hatching of viable eggs into larvae [14].

#### **4. Adulticides and Larvicides**

According to the World Health Organization (WHO) there are several types of vector control insecticides, divided into the following classes: organochlorines, organophosphates, carbamates, pyrethroids, bacterial larvicides, insect growth regulators and newly developed types such as neonicotinoids, spinosyns, and pyrroles [15].

Vector control programs directed to *A. aegypti* act to neutralize the adult populations using adulticides based on chemical products with an organophosphate or pyrethroid or carbamates and in the past, it was more popular to use organochlorine like DDT that has been gradually withdrawn in many countries based on environmental considerations being in use in areas of Africa and Southeast Asia with adequate results.

In the different regions, there has been an standardization of the methods to apply insecticides: residual spraying, space spraying, ITNs, treatment of nets (ITN-kits), and larviciding. Residual spraying a popular and commonly used method can be conducted indoors or outdoors. Indoor residual spraying consists of the application of residual insecticide products on indoor surfaces (e.g. walls) to kill vectors landing or resting on those surfaces; it is commonly used against indoor-resting mosquitoes [15].

Outdoor residual spraying commonly referred to as "perifocal treatment," consists of spraying the surfaces of breeding containers, with or without standing water, to obtain larvicidal and adulticidal effects on dengue vectors [15].

Space spraying, or fogging, produces insecticide-containing droplets that are small enough to remain airborne for some time [16] and are intended to cause a quick knock-down effect on flying or resting mosquito vectors upon direct contact. As low doses of chemical insecticides are used for space spraying, it does not leave a meaningful deposit that could have a residual effect [17]. Space spraying has been commonly used for the control of dengue outbreaks because of its efficacy against vector species, despite the lack of evidence of its effectiveness [15].

The use of adulticides has increased according to one of the most recent reports released by WHO for the period 2010–2019 from 434 tons in 2010 to 1680 tons in 2019 [15].

The stage of immature forms is also targeted with insecticide products generically called larvicides. The most common larvicide has been temephos, an organophosphate, but formulations with biological principles are becoming more frequent.

An interesting experience has been the use of limestone and salt in old tires laying on the patios. Tires are breeding sites that can persist positives for larvae and pupae all year long. In northern Honduras, the effect of these two products of domestic use was tested for the control of *A. aegypti* populations and the findings were highly promising, obtaining with salt a total of 112 days free of larvae and pupae, and after that time (without new treatments), a small number of larvae were produced per day (3 larvae per day compared to 15 larvae per day in control tires), which implies that with regular treatments of salt every 3 months an adequate control can be reached in these breeding sites.

When limestone (in powder) was used, the tires were kept free of larvae and pupae for 185–217 days in treated tires, and past that time without the new introduction of limestone, the production of the larval population remained minimum, which means applications of limestone can be used every 6 months to keep tires free of larvae [14].

Larvicide use of formulations based on organophosphate or pyrethroids is currently challenged by reports of resistance, and the use of salt and limestone has been mentioned as causing concerns about environmental contamination.

It is becoming more frequent to have reports of resistance to larvicides and adulticides, which represents an additional obstacle to adequate vector control [18, 19].

#### **5. Ovicides**

In a variation of the chemical control and the context of hygiene improvement, there has been a promotion of the method called little dab (la untadita) using a mixture of chlorine and detergent for the weekly cleaning of water deposits (cement tanks, cisterns, drums). This method improves the quality of deposit hygiene and has an ovicide effect on the eggs laid on the deposit walls. Days after the application of la untadita, this mixture remains with some repellent effect on the females getting to the deposits to lay eggs.

This technique was developed in 1994 based on traditional methods of cleaning water deposits but adding steps to direct the scrubbing of the walls to all surfaces covering them with a thin layer of detergent. It requires access to water to do it at least once a week and rinse it [13, 20]. See **Figure 2**.

#### **6. Biological control**

One of the prevalent ideas during several decades has been to use natural predators to destroy immature populations of *A. aegypti*. Predators such as larvivorous fishes (The biocontrol efficacy of six larvivorous fish species, namely, *Poecilia reticulata*, *Rasbora daniconius*, *Aplocheilus dayi*, *Oriochromis mossambicus*, *Oreochromis niloticus*, *Puntius bimaculatus*) and other similar species were tested in experimental conditions [21], another predator: Larvae of *Toxorrhynchites* sp. was also identified as effective at reducing larvae of *A. aegypti*. More recently *Bacillus turingiensis var israelensis* [22] and *Bacillus sphericus* (microbial agents and their spores) [23] have been also studied and found effective in experimental conditions acting as toxins for the larvae of the mosquito.

Copepods, small crustaceans, have been identified as effective predators in different studies in the Americas and Southeast Asian countries [24].

In Honduras during the first two decades of the current century, baby turtles of the species *Trachemys scripta elegans* [25, 26] have also been used for biological control of the *A. aegypti* larvae in small-scale field research sites.

Wolbachia is endosymbiotic bacteria capable of infecting some insect species including mosquitoes causing a reproductive phenotype called cytoplasmic incompatibility having as consequence the generation of inviable offspring when uninfected females mate infected males. If the female is infected this inviability does not occur, the Wolbachia infection can continue spreading in the population. The purpose of the Wolbachia infection from a control perspective is to interfere with the transmission of the dengue virus (DENV) to *A. aegypti* [27–29].

#### **7. Other types of control**

In an experimental process, there have been experiences modifying genetically the *A. aegypti* to produce offspring which die in the first days of life, and also the release of sterile males that, mating the females, do not produce any offspring [29].

Most of the new methods are used on a small scale and are undergoing the experimental stage and require to be implemented at the national level once they are authorized for extended use.

#### **8. Social and legal control**

Some countries have opted for severe fines for households keeping uncontrolled breeding sites or obstructing the work of vector control personnel. Such is the case of Singapore and Cuba [30–32].

In both countries, transmission of dengue has been relatively low during the last decades in comparison with their neighboring countries that suffer periodical epidemics. There is value in reaching a high level of vector control but the capacity to enforce strict regulation seems more viable in a small city-state like Singapore or countries with authoritarian regimes (both examples).

However, it is important that countries have a set of regulations and enforcement measures known by the population in order to prevent the transmission and reduce the number of trespassers that require legal actions.

The vector control programs require better support from the legal system when conflicts with the population limit their function.

#### **9. Measuring the vector control measures**

For close to a century, the control measures have been assessed using traditional entomological indexes such as: Container index, House index, and Breteau indexes corresponding to the measurement of the proportion of positive deposits in a visited section of a neighborhood, a city or town or any other concentration of houses, the number of positive houses or premises in an area, and the relationship of positive deposits and supervised houses [33, 34].

#### *Dengue Reduction through Vector Control DOI: http://dx.doi.org/10.5772/intechopen.109603*

Since the times of Fred Soper, there was an effort to reach indexes below 5% of positives as indicators of success, but even in highly controlled areas of Singapore with very low indexes, outbreaks of dengue have occurred [30, 31].

The limitation of the indexes is that they reflect the situation of a geographic area that is visited optimistically several times a year and in a more somber scenario once a year. They reflect the concentration of larvae in a container, which is not an accurate measurement of the potential of the breeding site to produce a healthy adult mosquito population. Different levels of mortality may depend on the container and its capacity to sustain larvae and pupae. Several studies prefer to calculate the presence of pupae because that stage does not need to feed in the container giving more predictability of the adult population to emerge from the breeding site, and they are 24 to 48 hours away from the emergences of adults that are at the active stage for the viral transmission (36). Traditional *A. aegypti* larval indices do not differentiate between containers in which all the immature stages are present and those which hold only first- and second-instar larvae. This means measuring pupae population represents an advantage [35].

A different way to measure both the activity of *A. aegypti* and the success of the vector control efforts is the installation of Ovitraps in sentinel sites to assess the oviposition activity of existing female *A. aegypti* in an area of study. The ovitrap itself and in combination with larvicides can be used as a control method [36].

There is an issue with measuring the success of vector control actions through traditional vectorial indexes stemming from the differences in the performance of anti-vectorial personnel, the capacity to cover broad areas of houses and identify correctly breeding sites sometimes with high levels of difficulty to be accessed.

In contrast to old-style vector control operations currently, we are facing increasingly large and explosive urbanizations in areas with poor infrastructure, deficient access to water, sanitation (and refuse systems) [11].

The advent of more complex methods of measurement based on statistical modeling requires to assess the relationship between entomological indexes and densities of adult mosquitoes in an area and the risk of transmission and to use the newly acquired computer technology in producing consolidates in real time to feed urgent decision making in vector control and identify areas of failure or success in real time.

#### **10. Community involvement**

Mosquito control has been in most countries a responsibility of the governments and the level of engagement from families and communities has been relatively low but recent studies demonstrate that there is great potential for population participation and collaboration in anti-vectorial control with the advantages of overcoming the logistic difficulty of visiting households to perform an effective control.

It is fundamental to the understanding of vector control that it has been traditionally managed in a vertical way taking as a model the Malaria and Yellow fever Campaigns of the beginning of twentieth century with a quasi-military hierarchical structure where all initiatives and directions followed a top-down format [6, 37].

During several decades, this vertical structure was functional without many challenges from the population and the members of the vector control structures but in the twenty-first century, there is a tendency to democratize the society and its organizations and to decentralize the decision process [38, 39].

One of the main challenges during the last quarter of the twentieth century and the first decades of the current one is the lack of cooperation with the procedures of source reduction that involve entering the patios, applying larvicides to water deposits, removing useless breeding sites (from the official perspective) that could have potential use for the household members.

How to deal with decreasing cooperation in the communities? There is a need to involve those same communities in the control of their own homes and communities [38]. The perception of vector control needs to be less of fulfilling an imposed and confused sanitary obligation and more of a clear routine to protect health and life of the family members.

The work of vector control now requires knowing more than just the dengue vector and more about the community dynamic, practices, and culture to design more effective and socially acceptable control.

Recent experiences in Latin America and South/South-East Asia for communitybased control have demonstrated that there are possibilities to apply innovation in vector control. Most of them have occurred because of a reassessment of the relationship between communities and their vector control [38].

Ethnographic studies have provided light on how perceptions of discardable, conservancy deposit management relate to cleanliness and hygiene aspirations in the family and their relation to disease, the need for health care/hospitalization, and risk of death [11].

As part of the knowledge required to improve vector control by the family is what are the social roles of the members in a family nucleus. The domains or responsibilities of mother and father need to be understood to be effective in tailoring effective messages to community members.

Depending on the culture, there are gender-based roles in the maintenance and elimination of potential breeding sites and this knowledge will provide a more clear effort to target the individuals in charge of keeping the containers free of mosquito sources [14].

The concept of hygiene and cleanliness needs to be linked in the communication to the preservation of health and the prevention of a spectrum of diseases and health disorders, and in this way, the removal or neutralization of breeding sites becomes relevant to the community as it is now to the vector control worker and the Ministry of Health.

Once vector control ceases to be important only for the vector control worker and the government institutions to some degree, it is important to operationalize a transference of responsibility to the individual, the family, and the community.

There are actions to be taken to transform the vector control of a routine in charge of the vector worker into a global effort that includes periodical cleaning-up campaigns helping neighbors to get rid of potential breeding sites (plastic objects, old metal pots, tires, cans, and similar) being careful not to stimulate the turn-over of old containers to brand new ones. As a personal testimony, many people observe that after a cleaning campaign, there is a tendency to replace those articles taken as refuse with new ones, and new breeding sites will be placed in the patios and backyards.

The second change in the vector control is to modify the profile of the vector control personnel into a more polyvalent profile, providing them a more comprehensive training to become more of an environmental care officer.

#### **11. Community involvement: Schools, neighbor associations, and local governments**

In the past, many public health programs were disease-specific and the members of the households were required to participate in programs that cause temporary or low motivation to them. In the case of dengue, the benefit for the household and the community seems to be scarce. Are they only acting for dengue control or does their participation lead to real family and community improvement?

Unless we are facing a dengue epidemic the main concern of the population is the nuisance of mosquitoes biting the house dwellers but they have more urgent needs to solve such as the perennial crisis with water supply, the accumulation of garbage, and the irregular refuse system or the total absence of one. Curiously, these felt needs are related to mosquitoes and dengue. There is a need to get a trade-off with community members to act on mosquito control as part of a more comprehensive package of community improvement measures.

Some communities facing the difficulty of getting rid of trash and other solid waste have organized themselves to pay individuals to mobilize their refuse in their own vehicles when the local governments are not able to do it. There is a real concern for the elimination of trash reinforced with the knowledge of dengue and similar mosquito-borne disease and the presence of their breeding sites in their homes.

Neighbor associations have demonstrated that if they identify a problem such as disease/s caused by mosquitoes, they are highly receptive to orientations leading them to take action, raise awareness in their own neighborhoods about control of trash and adequate control of water deposits, and even advocate for projects to provide better and more frequent water supply and wastewater systems.

In countries such as Honduras and Puerto Rico, there have been joint partnerships of the private and public sectors involved in the control of breeding sites and the School nucleus of teachers, parents, and students, which has been expressed in the production of educational material including textbooks and workbooks.

The development of school modules has followed a long process since the genesis of the idea as a research project in Latin American countries with a component of formative research, with rigorous measurement and the partnership of schools. Initially, the idea was to emphasize the dengue control component but later it was identified the need to incorporate environmental components based on the adequate water supply and the care required by the deposits containing water indoors and outdoors, and the component of adequate disposal of domestic waste. Finally, the last modules center on water deposits and solid waste more relevant to dengue control. More details were provided in the dengue module about concrete actions needed from parents and school-age children. The learning objectives were reached and the next step was the application of skills in the practical tasks of developing the actions of control in the family and with community members [40–42].

The Environmental School Program (PEA, for its Spanish acronym) is a dengue control initiative focused on primary schools that took place during 2005–2010 in several cities in Honduras. The environmental health program was designed to increase knowledge and develop skills in the identification and control of *A. aegypti* breeding sites, as well as in water and solid waste management [41] as mentioned before.

Incorporating through the school, young school children, their parents, and teachers can provide sustainability to a renewed vector control program targeting the action on dengue transmission but improving the environmental conditions at home and in peri-domestic spaces. Internalizing some values on domestic hygiene seems to be the route to long-term control.

Communities are also mobilized in the development of the activity called D-days when every household assumes the responsibility to clean their water deposit and eliminate discardable containers, and the government institutions provide support for an effective refuse system.

It is important to mention that experiences are crossing borders, and in many countries, the school system and the local government adjust experiences to their local circumstances. Scientific community has a role in supporting the development of innovative methods, diffusing them through scientific literature and institutional communications, and doing an appropriate and intense advocacy for the adoption of new techniques. Only an active scientific community can lead to changes in the routines of control and the assignment of more responsibilities to local authorities (decentralization) and empowerment to the population to take part in the reduction of the *A. aegypti* populations.

#### **12. Last comments: where do we go?**

Policy makers need to know that dengue is a recurrent problem for most countries, and the possibility to obtain an acceptable vaccine is still uncertain and the only known and used control method is vector control, which is potentially suitable as part of broader environmental health measures.

Paradoxically, we have as a result of a long tradition of vector control the emergence of a multiplicity of control methods that remain as collection of effective laboratory and field tests waiting to be taken to a national level, upscaling them in a careful but decided adoption.

It is not possible just to use one single method for vector control, but a combination of them according to needs, availability, and access of expertise by the personnel.

From experimental pilot, experiences are important to rescue the opening of different channels of communication with the communities through the vector-control workers, teachers, students, local governments and including the private sectors and grassroots organizations that have a real interest in all processes improving the life of citizens.

The vulnerability to dengue transmission comes in many places especially in poor neighborhoods because of the chronic lack of water supply, which presses the community dwellers to keep their water deposits that are necessary for their daily routines of cleaning/hygiene, laundry and more important for drinking and preparing their food. It is a common experience for vector control workers to witness the despair and anger of neighbors pressed to use larvicides in water deposits that change the appearance and odor of the water, or when forced to empty some positive deposits depriving them of water that is needed for them.

There is a need to link mosquito (*A. aegypti*) control to the development of programs to provide reliable water supply that will turn clean-up campaigns, temephos applications, or containers emptying from real nuisance to acceptable ways to protect family health.

In recent years, several epidemics of dengue and other *A. aegypti*-borne infections have affected the Americas, and South and South-East Asia, with outbreaks as well in the Pacific Islands and Africa. It is time that the national authorities are convinced

#### *Dengue Reduction through Vector Control DOI: http://dx.doi.org/10.5772/intechopen.109603*

that vector-control measures need to be redirected to be a tool for multi-disease control beyond only dengue and severe dengue. This would lead to alliances with other actors to combine control strategies and develop synergic actions that will have less opposition in the population and more strategic allies.

An area that is essential to the success of vector control is communication, and in an increasingly democratic world, the effectiveness of health programs is based on effective communication between institutions (Vector Control/Ministries of Health) and the population. Once many countries are passing from authoritarian regimes to more democratic institutions, the type of health communication needs to change from unidirectional to bilateral and multidirectional providing an opportunity to gather new ideas and needs from the population to optimize the implementation of new ideas for vector-control and community improvement.

Health policies related to dengue reduction and vector controls need to be shared with the national audiences in a clearer way, and to be open to observations, contributions, and dissent if that happens. As we have mentioned in this vector-control overview, there are many community issues that only solved will provide opportunities for a fully successful control.

There is an increasing level of understanding in the World Health Organization of the role of vector control in reducing dengue transmissions, and once a safe vaccine for all is reached, there must be an effort to use both approaches in a synergic approach. Previous discussions about abandoning the efforts of vector control once the vaccine was reached are practically over especially considering that vector control can have a synergic effect with the vaccine.

With the advent of other pandemic diseases like COVID-19 with more media attention, it is a priority to adopt new control strategies, and identify and integrate allies in the expanded approaches to reduce Aedes populations while a higher purpose: improvement of peridomestic spaces with less trash and wiser use of water containers is achieved.

#### **13. Conclusions**

Dengue is a viral infection with the main mode of transmission as vector-borne infection. Its clinical range goes from an asymptomatic infection to a severe lethal disease. We are relying on the prevention of dengue in effective control of the *A. aegypti* mosquito. There is a broad range of options for vector control but the most widely used are based on insecticides that are the cause of debate because of their potential environmental toxicity but also by their increasing report of resistance. Recent WHO reports state their use in the different world regions with variable levels of the result.

Most of the effort to control *A. aegypti* population concentrate on the reduction of breeding sites and the population of immature stages, while the use of adulticides is used when there are evidences of active transmission of infection and high densities of the mature adult mosquitoes (outbreaks of disease).

Currently, there are many studies on alternative methods that show high effectivity and efficacy when treating breeding sites, there is an urgency to implement the new methods outside of its research context adopting a more operational process.

Technology resources need to be applied to the challenges produced by unorganized urban growth, limited personnel, passive resistance to authoritarian styles to perform breeding sites assessment and control.

Modern times require new approaches including the adoption of new techniques for control, reviewing the profile of the vector-control worker and the organization in its entire structure, and a necessary process of relearning how to be more effective in interacting with the communities and the civic organizations.

Populations need to know better what is done in vector control in their own homes to turn a passive and sometimes hostile attitude into a more cooperative one, incentivizing their participation in the control through neighbors and civic organizations and as it is proposed through their school systems: learning and participating in their own domestic hygiene, which includes the vector's breeding site control.

There is a need to develop a more integrated approach with other disease-control programs and privileging a more decentralized process to perform disease control.

#### **Acknowledgements**

Special thanks to my colleagues at Brock University who provided me an opportunity to grow and look for some answers to the questions posed by this topic.

Thanks to my colleagues at the Americas Dengue Control Board who were actively asking and responding with their perspectives about some questions for dengue prevention and control.

Thanks to Neiby, Milan, and Ivan Fernandez who give me the chance to think about this topic with more realism.

#### **Conflict of interest**

The authors declare no conflict of interest.

#### **Author details**

Eduardo A. Fernandez Cerna1 \*, Catalina Sherman2 and Mercedes Marlene Martinez3

1 Brock University, St. Catharines, ON, Canada

2 Honduras Ministry of Health, Tegucigalpa, Honduras

3 Universidad Nacional Autonoma, Tegucigalpa, Honduras

\*Address all correspondence to: ecerna@brocku.ca

© 2023 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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#### **Chapter 15**

## Perspective Chapter: Hospital Disaster Management during Dengue Outbreak

*Ashis Shrestha*

#### **Abstract**

The outbreak of dengue results in surge of patient in the hospital. Dengue without warning signs are usually treated on outpatient basis while those with warning signs presents to emergency and are treated as inpatient basis. Severe dengue is treated in intensive care unit. This creates the challenge in managing the surge from outpatient to intensive care unit, often exceeding the capacity to treat. A hospital needs disaster management plan to cope with this surge of the patient. The disaster plan includes, hospital incident command system, networking plan, surge capacity, and emergency system. Beside this, a dynamic protocol needs to be implemented as sensitivity and specificity of the test kit remains same however, the predictive value of screening question increases as more and more population get affected. Therefore, primary or screening triage plays important during the surge of the patient.

**Keywords:** command system, dengue outbreak, disaster management, hospital, surge capacity

#### **1. Introduction**

Disasters are serious disruptions to the functioning of a community that exceeds its capacity to cope using its own resources [1]. Similarly United Nations International Strategy for Disaster Reduction (UNISDR) defined disaster as "a serious disruption of the functioning of a community or a society involving widespread human, material, economic, or environmental losses and impacts, which exceeds the ability of the affected community or society to cope using its own resources" [2]. A similar definition is used by World Health Organization. These are universally accepted definitions, and it holds true for a country, community, and hospital as well. Hospital's ability of cope using its resources is affected when the number of patient flowing in the emergency exceeds its capacity.

Disasters are caused by hazards which is "a process, phenomenon or human activity that may cause loss of life, injury or other health impacts, property damage, social, and economic disruption or environmental degradation" [3]. There are various type of hazards like environmental, technological, biological, etc. The risk of disaster is directly proportional to hazard and vulnerability. The vulnerability is "the condition determined by physical, social, economic and environmental factors or processed

which increase the susceptibility of an individual, a community, assets or system to the impacts of hazards" [4]. Hazard is not preventable; however, disaster can be prevented by managing vulnerability, known as risk management. The vulnerability of the hospital increases with poor hospital structure, uncoordinated patient flow and crowd control, absence of triage, inappropriate emergency management, and poor record-keeping system on normal days. Disaster is an escalation of normal day emergency; therefore, failing to manage daily emergency is failing to manage disaster.

There are four phases in disaster cycle, preparedness, prevention or mitigation, response, and recovery, **Figure 1** [5].

During the outbreak of dengue, the country, community, or a hospital responds to the event. The effort that is collectively put together in the response phase improves the response to some extent but not as desired. Therefore, for a good response, effort must be invested in the preparedness and prevention phases of disaster cycle. Similarly, recovery is an important phase after response.

The global burden of dengue has been rising in the last 30 years due to urbanization, climate change, and increased mobility. The rise is more in South-East Asia and South Asia [6]. A systematic review considering 262 outbreaks observed between 1990 and 2015 had 112 outbreaks after 2010, and the total number of patients since 1990 was 291,964 [7]. The patient with dengue presents with fever and myalgia and may require hospital admission for intravenous fluid. Out of patients visiting the hospital, nearly 40% require intravenous fluid [8]. This means an increase in the influx of patients visiting hospital and the number of admissions compared to normal days. This will cause a shortage of hospital beds, a shortage of medical supplies, and a risk of loss of revenue from cancelation of elective procedures. Moreover, the risk of nosocomial dengue has also been reported in health care workers [9, 10]. This surge will also cause exhaustion of health care worker. In a cross-sectional study, high burnout was observed in 15.9% of health care workers [11].

It is evident that the outbreak of dengue has been increasing in the last 30 years, causing a surge of patient in health care facilities overwhelming the service and

**Figure 1.** *Disaster cycle.*

#### *Perspective Chapter: Hospital Disaster Management during Dengue Outbreak DOI: http://dx.doi.org/10.5772/intechopen.110647*

human resources. This is a hazard leading to a challenge for space management for the patients' surge. Furthermore, in such conditions, it takes a lot of effort to maintain the supplies of fluid, medicine and blood products and ensure adequate Intensive Care Unit (ICU) beds are available [12]. Patient safety is compromised due to the pressurized health care system of the hospital. Therefore, risk management requires improving the response, which further requires improving preparedness. Planning the response, developing strategies, tactics, and implementation planning is important to improve the response.

#### **2. Hospital disaster preparedness and response plan**

Sendai framework for disaster risk reduction (2015–2030) priority 4 emphasizes enhancing disaster preparedness for effective response [13]. Therefore, a hospital requires multi-hazard hospital disaster preparedness and response plan. This plan will be useful in any type of disaster, including the outbreak of dengue infection. The outbreak of dengue will result in a shortage of space, unavailability of beds in critical care units, increased workload of the staff, and decreased quality of care for the patients [14]. This needs to be addressed in disaster management plan. Important components of hospital disaster management plan are as follows.

#### **2.1 Hospital incident command system**

The outbreak of dengue will last for several weeks; at the same time, the hospital also needs to manage regular daily patients. The hospital incident command system is the pillar of disaster management in the hospital [15]. Activation of hospital incident command. **Figure 2** will help in prioritizing and executing the task. The role and responsibilities of the individual are designated. The incident command is controlled by incident commander, who is the chief of the hospital. Planning for the management of the dengue and regular patient is done by planning officer. This includes communicating, coordinating, and managing staffs and space. The operational officer will coordinate clinical management and protocols. The logistic officer is responsible for maintaining supply–demand chain, while finance officer is responsible for financial planning.

The disaster management plan cannot cover all aspects of dengue management from the first to the last day. To manage the outbreak in a daily basis, incident action plan is prepared (IAP), **Figure 3** [16]. The action starts with incident notification and initial response, followed by incident command meeting. The incident command meeting prepares IAP, which is executed after operational briefing; this is called operational period. Once the operational period starts, preparation for next operation

**Figure 2.** *Hospital incident command system.*

**Figure 3.** *P diagram of Incident Action Plan.*

period is done considering the situation, information, and lesson learned during the preceding operational period.

#### **2.2 Networking plan: communication and coordination**

Networking plan is an important component of surge management in dengue. There are two types of communication that needs to be planned in preparedness phase. External and internal communication: the external communication includes the communication with the local authorities of the country and local stakeholders. This communication is necessary for case reporting and advocacy of the preventive measure. The prevention and control of the outbreak is an effective measure for decreasing the surge of the patient in the hospital. Moreover, during the surge of patient as the space of hospital is overwhelmed, other hospitals in the region of outbreak, which do not have full bed occupancy, can be used. This coordination needs prior planning. One of the models tested during COVID-19 is the hub and satellite model [17]. Hospitals in the country are divided into hub according to the region and its resources; the hospitals that are near hub hospitals are categorized as satellite hospitals. A communication and coordination protocol for hub and satellite hospitals to support each other during the disaster is established during the preparedness phase [18]. Internal communication requires a communication officer with lists of contacts of all hospital staffs. Staffs needs to be informed about the communicable potential of dengue, the precaution to be taken, and the protocols of clinical case management and surge management needs to be informed to all hospital staffs.

#### **2.3 Surge capacity**

During the outbreak of dengue, most patients visiting outpatient department can be sent home, and some patients visit emergency and require fluid management along with

#### *Perspective Chapter: Hospital Disaster Management during Dengue Outbreak DOI: http://dx.doi.org/10.5772/intechopen.110647*

admission. In an observational study, outpatient treatment was needed in 82% of patient, and 18% required hospital admission. Intravenous fluid resuscitation was required in 3.2% of the patient [19]. A systemic review published in 2019 summarizes that the countries' dengue endemic has seasonal surges in the hospital; they have early warning system, therefor they cope with the surge by temporary expansion of the surge. The expansion includes, space, human resources, laboratory services, funds, and logistics. However, in non-endemic countries, surge are managed by reverse triaging. Therefore, context-specific planning will help hospitals cope with the surge of patient during dengue epidemics [12]. All hospitals face challenges in their ability to meet the surge demand. Larger hospitals in regional settings usually operate near capacity, while smaller hospitals at local level operate with limited availability of resources. Therefore, coping with surge is a challenge for all hospitals and needs to be planned during planning phase of disaster cycle [20].

Key components of surge planning include four S's: Structures, Staff, Stuff, and System [21]. Sub-acute units in the hospitals should be identified as it is much easier to manage the outbreak if it can be managed inside the facility. However, if the facility is unable to meet the demand of surge the spaces outside the facility need to be considered [22]. Expansion of the space requires effective management of staffs and stuffs. There should be interdepartmental coordination to manage the staffs from the department that does not have a patient load; moreover, hub and satellite [18, 23] mechanism is also helpful to mobilize staffs from the hospitals that are not expecting surge of patients. Moreover, equipment required to expand the capacity, needs to be planned. The equipment may include ward bed, ICU bed, medications, and logistic supplies [21]. An effective multi-hazard management plan must describe the system with a clear guiding policy in case of surge of patients.

#### **2.4 Emergency system**

Emergency system of the hospital needs to be functional on a daily basis because disaster is an escalation of everyday work. During disaster, it is not possible to implement a new system that has never been in practice. Therefore, hospital requires planning of outpatient services and emergency services. Management of the patient at triage, emergency and inpatient ward, and ICU must be well coordinated. The essential component of efficient management is a functional triage system. A primary and secondary triage is required to sort out and prioritize patients. Primary triaging is a system based on questionnaire. During the outbreak of dengue, the primary triage may contain questions like, "Do you have fever?" If the answer is yes, then the patient goes to dengue suspect zone, however, if the answer is no, then the patient goes to regular outpatient or the emergency. Once the patient is sent to the dengue suspect zone, secondary triaging is done, where patients are triaged based on symptoms and signs and labeled as critical or non-critical [24]. During the outbreak of dengue, the surge of the patient might interrupt the services for the patient with other clinical conditions presenting in outpatients, emergencies, and inpatient. Therefore, a separate unit consisting of dengue emergency, outpatient, inpatient, and critical care patient needs to be planned [25]. Even countries with infectious disease hospitals may be overwhelmed with the surge of the patient causing overflow of the patient to other hospitals.

#### **3. Protocols**

Protocols are important for the consistency of the service delivery. There is WHO management available for dengue management [26]; moreover, every

dengue-endemic country will have national guidelines. These guidelines are more static and are based on recently available evidence. Every healthcare institution needs to have a protocol based on these guidelines. These are operational, brief, and dynamic documents. During the dengue outbreak, the protocols are adjusted based on the clinical evidence for patient safety and surge of the patient. Therefore protocol needs to be dynamic and needs to be changed according to the situation [27].

Fever is the most common presentation of dengue followed by myalgia [19, 28]. For all patients with fever, the screening is done by rapid diagnostic kits that detect NS1 antigen and IgM antibodies. The NS1 antigen is detectable the most within the first 2–4 days, and IgM antibody after that. During this period, the sensitivity of the kit to detect NS1 ranges from 63% to 73%, while that of NS1 and IgM combine ranges from 90% to 98% [29–32]. The important phenomena, is that the sensitivity and specificity of the test kit remains same however, the predictive value of screening question increases as more and more population get affected [33]. As laboratories are overwhelmed with the surge of the investigation, it becomes very difficult to process the test in time, affecting sick patients whose clinical diagnosis is in a dilemma. Therefore, at the peak of outbreak, we may not need to send investigations for all patients who do not have warning signs. Hence, a small change in protocol for investigation or management will cause huge relief of workload to the hospital during an outbreak.

Dengue virus can present with severe cases and mortality in 1–5% of cases. The important laboratory finding of dengue fever is thrombocytopenia [34]. Platelet counts are useful in predictive and recovery parameters of dengue fever, dengue hemorrhagic fever, and dengue shock syndrome [35]. Studies suggest a high risk of bleeding below a platelet count of 20,000/cumm and a moderate risk below 21–40,000/cumm [36]. The cut-off value of less than 46,500/cumm has also been taken to stratify the risk of bleeding [37]. Platelets transfusion is found to be done in some literature [19], however, it has not been proven to be effective in preventing the development of severe bleeding or shortening the time to the cessation of bleeding [38]. Therefore, this type of information needs to be analyzed carefully and must be on the basis of the best available evidence before applying it to protocol. During the outbreak of dengue, the protocol must be customized so that it does good to maximum number of patients.

#### **4. Capacity building in clinical case management**

It is necessary that health care workers have a good knowledge of dengue infection. A health care worker in a hospital must know the screening criteria, treatment criteria, reporting procedures, and preventive knowledge. The knowledge does not always translate to the adoption of preventive measures [39].

Training on infection prevention and control are necessary while orientation on protocol is important to ensure that all staffs have uniformity in action. Moreover, during the outbreak of dengue, individual roles and responsibilities must be understood by each staff. This can be achieved by simulation exercises. There are various types of exercises that can be planned according to preparedness of the hospital [40]. Tabletop exercise can be done to test the dengue outbreak management plan. The plan is adjusted and finalized according to the lesson learned from the tabletop exercise. After finalization of the plan, functional components of the plan like primary and secondary triage can be tested by drill. Similarly, drill can also be done with clinical

*Perspective Chapter: Hospital Disaster Management during Dengue Outbreak DOI: http://dx.doi.org/10.5772/intechopen.110647*

case management and reporting system. The coordination and communication can be tested with functional exercise. Finally, full scale simulation exercise can be planned during the preparedness phase.

Besides this online learning has been one of the effective ways of learning following the COVID-19 crisis. Online learning is no more an option, but it is a necessity [41]. During the surge of dengue patient, the event will exhaust human resources. It will be difficult to manage health care workers' time for educational sessions. This method of learning can be adopted during time of crisis. However, inventing new methods during the crisis is not helpful; therefore, online sessions must be part of professional development for health care workers.

Social media is yet another powerful way of disseminating information. This platform can be used for short messages or updates. During disaster, there are three types of social media users: influential social media creators, followers, and social media inactive [42]. Social media is used as reporting system, distributed problem-solving, and digital volunteerism [43].

#### **5. Database system**

The surge of dengue outbreaks can be managed effectively by maintaining proper database system in the hospital. The real-time data will help in planning human resources and logistics. Moreover, predictive analysis can be done to anticipate the actions that need to be taken in future days. There are some important variables that will provide crucial information for patient management. For example, the number of cases per day will identify the trend of the dengue, and the address of the patient presenting will help identify the outbreak area. This will further help in the control of the disease. Likewise, the presenting symptom of the patient is helpful in understanding the pattern of presentation. This is important during the surge of the patient when the diagnostic facility is overwhelmed, and decisions have to be made on the basis of clinical findings for non-severe cases.

Data without analysis is not useful; therefore, a system of analyzing and providing the information to the concern in a useful and understandable way is important. This system must be in place prior to the crisis. The activities that are habitual and are in

#### **Figure 4.**

*Sample of dashboard used during COVID-19 pandemic.*

daily practice work well during the crisis. One way of working is by using a dashboard that is visible to all clinicians, **Figure 4**. Moreover, hospitals should also have the capacity to collect data from external sources, which means the events that are being reported from other hospitals, recent advances, and updates. The process of acquisition of internal and external information, and its analysis to produce a meaningful information is an essential component of disaster management [44].

Research is another integral part of disaster management. Researches can be planned in two phases: during preparedness and response phases. In countries where dengue is endemic, response researches can be pre-planned. This will help prepare for subsequent outbreaks and improve the response.

#### **6. Conclusions**

Dengue is an infectious disease that can potentially exceed the hospital's capacity to provide the service. This surge of the patient can be managed by disaster management plan. Every hospital must have a disaster management plan including the hospital's outbreak management components. The four phases of disaster cycle need to be addressed well. An investment of effort in preparedness will improve the response phase of the disaster.

### **Conflict of interest**

None.

#### **Notes/thanks/other declarations**

None.

#### **Acronyms and abbreviations**


*Perspective Chapter: Hospital Disaster Management during Dengue Outbreak DOI: http://dx.doi.org/10.5772/intechopen.110647*

#### **Author details**

Ashis Shrestha Patan Academy of Health Sciences, Lalitpur, Nepal

\*Address all correspondence to: ashisshrestha@pahs.edu.np

© 2023 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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### *Edited by Márcia Aparecida Sperança*

*Dengue Fever in a One Health Perspective - Latest Research and Recent Advances* presents studies on dengue fever (DF) and dengue virus (DENV) that discuss eco-epidemiology, physiopathology, and new biotechnological tools to fight against this important disease in the context of the World Health Organization's One Health strategy. The book is organized into five sections: "Epidemiological Aspects", "Environmental Aspects", "Pathogenicity", "Diagnosis and Treatment" and "Management Strategies". The chapters address topics such as DF prevalence and management in a Chinese county, the risk of DF in American children younger than 15 years, the silent transmission of DENV by asymptomatic individuals, the use of X-ray and ultrasound to identify severe DF cases, gene-silencing techniques to investigate biological aspects of DF, viral genomic surveillance to promote early intervention in DF epidemics, and much more.

> *Alfonso J. Rodriguez-Morales, Infectious Diseases Series Editor*

> > ISBN 978-1-80356-923-9 ISSN 2631-6188 ISBN 978-1-80356-925-3

Dengue Fever in a One Health Perspective - Latest Research and Recent Advances

IntechOpen Series

Infectious Diseases, Volume 22

Dengue Fever in a

One Health Perspective

Latest Research and Recent Advances

*Edited by Márcia Aparecida Sperança*

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