Dengue hemorrhagic fever is a severe, often fatal, complication of dengue fever. Dengue and dengue hemorrhagic fever are caused by any of the dengue family of viruses. Infection with one virus does not protect a person against infection with another. Dengue is spread by the bite of an Aedes mosquito. The mosquito transmits the disease by biting an infected person and then biting someone else.
Dengue viruses occur in most tropical areas of the world.
Dengue is common in Africa, Asia, the Pacific, Australia, and the Americas. It is widespread in the Caribbean basin. Dengue is most common in cities but can be found in rural areas. It is rarely found in mountainous areas above 4,000 feet. The mosquitoes that transmit dengue live among humans and breed in discarded tires, flower pots, old oil drums, and water storage containers close to human dwellings.