Dengue fever is a debilitating and sometimes hemorrhagic fever (one that is associated with extensive internal bleeding). The disease is caused by four slightly different types of a virus from the genus Flavivirus that is designated as DEN. The four antigenic types are DEN-1, DEN-2, DEN-3, and DEN-4.

The dengue virus is transmitted to humans via the bite of a mosquito. The principle mosquito species is known as Aedes aegypti. This mosquito is found all over the world, and, throughout time, became adapted to urban environments. For example, the mosquito evolved so as to be capable of living year round in moist storage containers, rather than relying on the seasonal patterns of rainfall. Another species, Aedes albopictus (the "Tiger mosquito"), is widespread throughout Asia. Both mosquitoes are now well established in urban centers. Accordingly, dengue fever is now a disease of urbanized, developed areas, rather than...