INFECTIOUS DISEASES Medstudents' Homepage Dengue/Dengue Hemorrhagic Fever Introduction: Dengue fever is an acute febrile infectious disease, caused by all four serotypes (1, 2, 3 or 4) of a virus from genus Flavivirus, called dengue virus. Its the most prevalent flavivirus infection of humans, with a worldwide distribution in the tropics and warm areas of the temperate zone corresponding to that of the principal vector, Aedes aegypti. When simultaneous or sequential introduction of two or more serotypes occurs in the same area, there may be an increased number of cases with worse clinical presentation (dengue hemorrhagic fever). The term hemorrhagic is imprecise, because what characterizes this form of the disease is not the presence of hemorrhagic manifestations, but the abrupt increase of capillary permeability, with diffuse capillary leakage of plasma, hemoconcentration and, in some cases, with non-hemorrhagic hypovolemic shock (dengue shock syndrome). Epidemiology: The highest incidence of dengue is in southeast Asia, India and the American tropics, where A. aegypti can be found. In the 1980s, dengue emerged in explosive epidemics in Rio de Janeiro (1986 - serotype 1 and 1990 - serotype 2 was isolated in Niterói city), São Paulo and in many other towns and cities in Brazil. In areas such as southeast of Asia, where all four dengue virus types are hyperendemic, children are almost exclusively affected, and seroprevalence approaches 100% by young adulthood. Transmission occurs by the bite of Aedes aegypti female mosquitoes - the same vector of urban yellow fever - a day-active species with low fly-autonomy that is abundant in and around human habitations. In Brazil and other countries Aedes albopictus may also be responsible for transmission. Viremic humans (till the fifth day of disease) serve as the source of virus for mosquito infection; there is not person-to-person transmission. Movement of viremic humans provides the principal means of spread, and rapid air travel is a factor in most recent epidemic emergences. | |
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