**6. Clinical aspects**

The most commonly occurring DENV infection transits through an asymptomatic or mildly symptomatic course [38]. Symptomatic dengue fever is usually accompanied by headache, malaise, retroorbital pain, arthralgia, and myalgia with a severity that honors "break-bone" fever alternative name of this disease. It lasts from three to 7 days. A small fraction of these patients evolve to the life-threatening clinical form of severe dengue, usually preceded by the appearance of warning signs (see below). All the four viral serotypes cause resembling disease symptoms.

In comparison to the previous 1997 version, the WHO revised classification of 2009. This makes more precision towards sensitivity and specificity of dengue cases. While being reported having changed dengue features with the passage of time during treatment; the dengue affected patients are categorized in Group A or Group B. More concern is recommended if symptoms becoming serious for next step of necessary hospitalization [39, 40]. As WHO 1997 version already includes plasma leakage and bleeding; but, however, the WHO 2009 classification entails target monitoring and organ impairment exhibiting the situation more clearly towards future dengue disease cure. Group C category of dengue patients has been explained in a better way in revised classification of WHO version 2009. This version, indeed is a practical guidance and very much helpful in dengue endemic areas especially where medical facilities are lacking. It is worth mentioning that WHO 2009 classification also highlights the other co-existing factors such as pregnancy, child and old age, diseases like diabetes and various social circumstances [41].

The WHO 2009 revised dengue classification stratifies disease into the following:


causative agent of broadly analogous disease spectrum in humans [29–31]. It consists of ten proteins, out of which three proteins, capsid (C), membrane (M), and envelope (E), play structural role and seven (NS1, NS2A, NS2B, NS3, NS4A, NS4B and NS5) are identified as non-structural that direct DENV replication. Approximately 17% of these virions are lipid by weight which forms a lipid bilayer between E/M outer shell and the nucleocapsid core [32, 33]. Binding of dengue virus like most of the other viruses to its receptor is regulated by envelop protein (E). In mammalian cells, all the serotypes binds with nLc4Cer, DC-SIGN/L-SIGN, Heparan sulfate as well as Mannose receptors. Additionally DENV-2 serotype also show binding trend with HSP70/HSP90, CD14-associated protein, GRP78 and two other unknown protein receptors. On the other hand DENV 1–3 serotypes can also attach with Laminin receptor while DENV 2–4 serotypes are also found to bind with protein receptor which is unknown [34]. After binding with particular receptors through receptor-mediated endocytosis, virion fuses with acidic lysosomes. Then, the viral particle releases its RNA in the cytoplasm of host cell for the synthesis of viral proteins. After the synthesis of all the required proteins, viral RNA starts generating a minus strand, and then transcription of new plus stranded molecule occurs. Hundreds of copies of viral particles are generated from a single virus particle leading towards cellular damage and even death. RNA-dependent RNA polymerases (RdRps) encoded by the virus itself and other cellular factors catalyze the infection cycle of this virus

**Figure 4.** Lifecycle of *Aedes aegypti* (http:/www.ipnc.nc/FCKeditorFiles/Image/entomo\_20.jpg).

8 Dengue Fever - a Resilient Threat in the Face of Innovation

Furthermore, three categories have been described in 2 WHO scheme of dengue-affected patients:


**iii.** Group C includes patients with severe plasma leakage, severe bleeding leading towards extreme condition of organ impairment [41].

in the market for the protection of people including young children, pregnant women, old

Dengue Fever: A General Perspective http://dx.doi.org/10.5772/intechopen.81277 11

The best way to control dengue is to improve capabilities of mosquito abatement especially in the most populated areas where vector densities are high due to availability of hosts [18].

Public awareness counts in integrated pest management at a significant level, various examples can be sited from the literature when community efforts played a role for the eradication of disease agents. As *Aedes aegypti* was eliminated from countries various regions of the USA during the 1960s when relatively well funded eradication campaign supported by a high degree of political and community were involved. The effective collaboration of a welleducated society with the assistance of mosquito control well-trained staff will be the most compelling and economically reliable method for the removal of *Aedes albopictus* populations

The vector borne diseases are controlled worldwide, simply via controlling the vector. This thumb rule equally implies on dengue vector *Aedes* mosquitoes as well. Integrated Vector Management (IVM) mostly focuses on chemical control using insecticides; most frequently used are reported organophosphates and pyrethroids by WHO against dengue, malaria as well as yellow fever. These insecticides are affective against larvae, pupae and adults as well [25, 56, 57]. No new public health insecticides have been developed for mainstream vector control in disease-endemic countries (DECs) for the last three decades. Narrow range of public health insecticides necessitates new, safe, less expensive, environment friendly insecticides to replace those already being commercially used and mostly have been reported to develop resistance. Pyrethroid insecticides such as Permethrin, Deltamethrin, Cypermethrin, Cyhalothrin, etc. and DDVP organophosphate insecticides have been frequently used against mosquitoes and flies at household level. However, pyrethroid insecticides are reported to develop resistance. Hence, synergistic use of organophosphae and pyrethroid insecticides is being used now-a-days in order to combat this resistance menace [58]. New insecticides which are safe for health and environment as well demand investment. It is estimated that about US\$70 million amount is required to develop a new insecticide. Public health insecticide market encompasses about US\$151.2 million worldwide, hereby, shows the overall small size market. It is a dire need of time to engage commercial partners in the development of new insecticides. It has been suggested that both commercial and academic partners must collaborate and work together. In addition, community level health workers must be stimulated

people [55].

**9. Control of vector** *Aedes*

**10. Public awareness**

in rural and suburban regions [18].

**11. Chemical control**

The classification is meant to make it realized that the group is clearly identified so that patients are going to be treated keeping in view the relevant category.
