Dengue is prevalent throughout the tropics and subtropics. Outbreaks have occurred recently in the Caribbean, including Puerto Rico, the U.S. Virgin Islands, Cuba, and Central America. Cases have also been imported via tourists returning from areas with widespread dengue, including Tahiti, Singapore, the South Pacific, Southeast Asia, the West Indies, India, and the Middle East (similar in distribution to the areas of the world that harbor malaria and yellow fever). Dengue is now the leading cause of acute febrile illness in U.S. travelers returning from the Caribbean, South America, and Asia.

A 2009 outbreak of dengue fever in Key West, Fla., showed that three patients who did not travel outside of the U.S. contracted the virus. Subsequent testing of the population of Key West has shown that up to 55 of the people living in the area have antibodies to dengue. As of July 17, 2010, 17 individuals have been identified that acquired dengue in Key West in 2010.

Dengue fever is common, and statistics show it may be increasing in Southeast Asia. Thailand, Vietnam, Singapore, and Malaysia have all reported an increase in cases. According to the U.S. Centers for Disease Control and Prevention (CDC), there are an estimated 100 million cases of dengue fever with several hundred thousand cases of dengue hemorrhagic fever requiring hospitalization each year. Nearly 40% of the world's population lives in an area endemic with dengue.

How is dengue fever contracted?

The virus is contracted from the bite of a striped Aedes aegypti mosquito that has previously bitten an infected person. The mosquito flourishes during rainy seasons but can breed in water-filled flower pots, plastic bags, and cans year-round. One mosquito bite can inflict the disease.

The virus is not contagious and cannot be spread directly from person to person. There must be a person-to-mosquito-to-another-person pathway.