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Dengue, an arboviral disease, is an arthropod-borne viral infection of humans. Arboviruses consist of a group of animal viruses that are able to reproduce in an arthropod and can be transmitted to a vertebrate host. Because of the degree of morbidity and mortality involved, dengue is considered the most important arboviral disease affecting humans. The four dengue virus serotypes, designated 1, 2, 3, and 4, are ribonucleic acid (RNA) viruses belonging to the genus
Flavivirus of the family Flaviviridae. Epidemics of dengue fever in urban communities are explosive and involve significant portions of the population. They often start during the rainy season, when the vector mosquito,
Aedes aegypti, is in abundance and thriving in urban areas.
According to the World Health Organization “arboviruses are viruses that are maintained in nature principally, or to an important extent, through biological transmission between susceptible vertebrate hosts by hematophagous arthropods or through transovarial and possibly venereal transmission in arthropods; the virus multiply and produce viraemia in the vertebrates, multiply in the tissues of arthropods, and are passed on to new vertebrates by the bites of arthropods after a period of extrinsic incubation.” Vertical (transovarial) and venereal transmission in arthropods may serve as basic long-term maintenance mechanisms for some arboviruses. Some researchers consider vertical transmission to be a survival mechanism developed by the virus to resist adverse climatic conditions that may affect its arthropod host. Vertical transmission involves the direct transfer of infection from a parent organism to his, her, or its offspring. In contrast, horizontal biological transmission involves ingestion of the virus in the blood of a viremic vertebrate, multiplication of the virus in the midgut of the mosquito, dissemination of the virus to the hemocoel, infection of the salivary glands, and transmission of the virus to a susceptible vertebrate host by the mosquito's bite. The virus can also be transmitted either horizontally by arthropods infected vertically, or mechanically by arthropods that obtain a partial blood meal from an infected host and then continue they’re feeding on a susceptible one.
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