There are four distinct but closely related dengue virus serotypes (of the genus Flavivirus) that cause dengue fever; named DEN-1, DEN-2, DEN-3, and DEN-4. Infection with dengue viruses produces a spectrum of clinical illness ranging from a nonspecific viral syndrome to severe and fatal hemorrhagic disease. Infection with one serotype does not provide cross-protective immunity to the other three types, so people living in a dengue-endemic area can be infected by the four dengue virus serotypes during their lifetimes. As there is no specific treatment for dengue fever, it is essential to identify the strain of the infecting virus, immune status and predisposition of the patient as early as possible.