**1. Epidemiology of dengue and the coastal El Niño phenomenon in Peru and Ecuador**

#### **1.1 Epidemiological data**

Coastal El Niño is a weather phenomenon that is caused by abnormal warming (above 0.4°C) of the Pacific Ocean waters near the coasts of Ecuador and Peru, and it can even reach the central and southern Peruvian coasts. As a result, it produces intense rains that, in turn, cause overflow of streams, floods, and allow the accumulation of stagnant waters, which forms the ideal scenario for the appearance of outbreaks of vector-borne diseases such as dengue (DENV), other arbovirosis, and zoonotics such as leptospirosis [1–4]. This phenomenon was presented more clearly in the summer of 2017; however, rains and floods have been reported for Peru even since December 2016 [5].

As a result of the climatic phenomenon, the *Aedes aegypti* vector (which in turn is a vector of chikungunya and Zika [ZIKV] fever) had been quickly installed in 448 districts of Peru, where more than 14 million people live, by July 2017 [6]. Thus, the Peruvian State in June 2017, declared emergency in 10 regions, which reported 231,874 victims; 1,129,013 affected and 143 dead. It is necessary to know this, because the direct impact of the weather phenomena contributes to the dengue vector conditioning, facilitating its dissemination with ease. Thus, the Peruvian Ministry of Health reported that at the end of 2017, the epidemiological surveillance system reported 76,093 cases of dengue (among probable and confirmed), marking an increase of up to three times more cases compared to 2016 (25,236 cases) (**Figure 1**) [7].

Among the most frequently reported forms were dengue without warning signs (88.6%), dengue with warning signs (11%), and severe dengue (0.3%). The cumulative national incidence for 2017 was 239.1 cases per 100,000 inhabitants and there were 93 deaths, of which 79 were confirmed cases and 14 were probable [8].

There was a marked increase in cases, in those places where there was a greater presence of rain and floods. Thus, for example, Piura concentrated 64% of dengue cases: this place being one of the most affected cities and even presented an overflow from its main river that crosses through the same city, the river Piura [9].

Do not forget that northern Peru is an endemic area due to climate, geography, and other factors that make it a vector-friendly ecosystem, being considered one of the countries with the greatest impact due to climate change [10].

#### **1.2 Dengue and climate**

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. The incidence of dengue is very seasonal; this seasonality is the footprint of local meteorological variables, which also vary seasonally, and their impact on the demographics of mosquito vectors and transmission dynamics [11].

#### **Figure 1.**

*Number of dengue cases, according to epidemiological weeks. Peru, 2013–2017. Taken from: Ministry of Health of Peru MINSA [12].*

**35**

**Figure 2.**

*of Peru MINSA [17].*

*Situation of Dengue after the Phenomenon of the Coastal El Niño*

The geographical and climatic conditions of the cities most affected by the El Niño Costero phenomenon turned them into zones of epidemics; in these places, there is an important population growth, from urbanization to sectorization in young towns, urban slums, where in many there is no basic infrastructure and water supply is insufficient, which requires temporary water storage, as well as high temperatures, migratory movement, and beaches with influx of people, which make not only dengue proliferate but also other arbovirosis such as chikungunya [13].

The propagation of the vector for decades is conditioned by the climatic changes. For example, in May 2004, heat waves and droughts were observed in the coastal areas of Kenya, toward Lamu and Mombasa, two large coastal cities. That period was also the beginning of a large chikungunya outbreak in these two cities (with reported attack rates of 75%) before its spread to the Indian Ocean [14]. Entomologists have explained how and why droughts can be associated with increases in diseases transmitted by *Aedes*, such as chikungunya, dengue, Zika, and yellow fever [15, 16]. During droughts, due to water scarcity, people store a greater amount of water outside or inside the home for longer periods of time, providing

In Peru, the consequence of this weather phenomenon allowed the dissemination of the *Aedes* vector and consequently led to the increase in cases of emerging diseases, such as Zika and chikungunya (**Figure 2**). Thus, from 2016 to 2018, 1113 gestating women entered the surveillance system for Zika, of which 61% were notified in 2017. Of the total number of pregnant women notified, 31% had laboratory confirmation for Zika virus through molecular tests like polymerase chain reaction-

The fluvial precipitations that the phenomenon of the coastal El Niño brought with it during 2017 triggered the collapse of the sewerage system, generating floods and the exposure of wastewater, which together with the rains gave an adequate

*Distribution of indigenous cases of Zika by onset of symptoms. Peru 2016–2017. Taken from: Ministry of Health* 

*DOI: http://dx.doi.org/10.5772/intechopen.92095*

**1.3 Epidemiology of other metaxenic diseases**

shelters to mosquito eggs and larvae [13].

reverse transcription (RT-PCR) [7].

**1.4 Dengue and coinfections**

*Dengue Fever in a One Health Perspective*

cases) (**Figure 1**) [7].

**1.2 Dengue and climate**

As a result of the climatic phenomenon, the *Aedes aegypti* vector (which in turn is a vector of chikungunya and Zika [ZIKV] fever) had been quickly installed in 448 districts of Peru, where more than 14 million people live, by July 2017 [6]. Thus, the Peruvian State in June 2017, declared emergency in 10 regions, which reported 231,874 victims; 1,129,013 affected and 143 dead. It is necessary to know this, because the direct impact of the weather phenomena contributes to the dengue vector conditioning, facilitating its dissemination with ease. Thus, the Peruvian Ministry of Health reported that at the end of 2017, the epidemiological surveillance system reported 76,093 cases of dengue (among probable and confirmed), marking an increase of up to three times more cases compared to 2016 (25,236

Among the most frequently reported forms were dengue without warning signs (88.6%), dengue with warning signs (11%), and severe dengue (0.3%). The cumulative national incidence for 2017 was 239.1 cases per 100,000 inhabitants and there

There was a marked increase in cases, in those places where there was a greater presence of rain and floods. Thus, for example, Piura concentrated 64% of dengue cases: this place being one of the most affected cities and even presented an overflow from its main river that crosses through the same city, the river Piura [9].

Do not forget that northern Peru is an endemic area due to climate, geography, and other factors that make it a vector-friendly ecosystem, being considered one of

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. The incidence of dengue is very seasonal; this seasonality is the footprint of local meteorological variables, which also vary seasonally, and their impact on the demograph-

*Number of dengue cases, according to epidemiological weeks. Peru, 2013–2017. Taken from: Ministry of Health* 

were 93 deaths, of which 79 were confirmed cases and 14 were probable [8].

the countries with the greatest impact due to climate change [10].

ics of mosquito vectors and transmission dynamics [11].

**34**

**Figure 1.**

*of Peru MINSA [12].*

The geographical and climatic conditions of the cities most affected by the El Niño Costero phenomenon turned them into zones of epidemics; in these places, there is an important population growth, from urbanization to sectorization in young towns, urban slums, where in many there is no basic infrastructure and water supply is insufficient, which requires temporary water storage, as well as high temperatures, migratory movement, and beaches with influx of people, which make not only dengue proliferate but also other arbovirosis such as chikungunya [13].
