Dengue/Dengue Hemorrhagic Fever: The Emergence of a Global Health Problem

Dengue and dengue hemorrhagic fever (DHF) are caused by one of four closely related but antigenically distinct virus serotypes (DEN-1 DEN-2 DEN- 3 and DEN-4) of the genus Flavivirus. Infection with one of these serotypes does not provide cross-protective immunity so persons living in a dengueendemic area can have four dengue infections during their lifetimes. Dengue is primarily an urban disease of the tropics and the viruses that cause it are maintained in a cycle that involves humans and Aedes aegypti a domestic day-biting mosquito that prefers to feed on humans. Infection with a dengue virus serotype can produce a spectrum of clinical illness ranging from a nonspecific viral syndrome to severe and fatal hemorrhagic disease. Important risk factors for DHF include the strain and serotype of the virus involved as well as the age immune status and genetic predisposition of the patient. The first reported epidemics of dengue fever occurred in 1779-1780 in Asia Africa and North America; the near simultaneous occurrence of outbreaks on three continents indicates that these viruses and their mosquito vector have had a worldwide distribution in the tropics for more than 200 years. During most of this time dengue fever was considered a benign nonfatal disease of visitors to the tropics. Generally there were long intervals (10-40 years) between major epidemics mainly because the viruses and their mosquito vector could only be transported between population centers by sailing vessels. (excerpt)