Definition of Dengue hemorrhagic fever:

Dengue hemorrhagic fever is a severe, potentially deadly infection spread by certain mosquitoes (Aedes aegypti ).

See also: Dengue fever

Causes, incidence, and risk factors:

Four different dengue viruses have been shown to cause dengue hemorrhagic fever. This condition occurs when a person catches a different dengue virus after being infected by another type sometime before. Prior immunity to a different dengue virus type plays an important role in this severe disease.

Worldwide, more than 100 million cases of dengue fever occur every year. A small number of these develop into dengue hemorrhagic fever. Most infections in the United States are brought in from other countries. It is possible for a traveler who has returned to the United States to pass the infection to someone who has not traveled.

Risk factors for dengue hemorrhagic fever include having antibodies to dengue virus from prior infection and being younger than 12, female, or Caucasian.