Yellow Fever

Cause, Transmission & Environments

Yellow fever is an acute viral disease of varying severity. Currently occurs in portions of South America and Africa. Two forms of yellow fever exist: the urban, and the sylvatic/jungle. Although two forms are clinically and etiologically identical, their epidemiology is different. Urban yellow fever is an epidemic viral disease of humans transmitted from infected to susceptible persons by the bite of Aedes aegypti mosquitoes. Aedes aegypti mosquitoes breed in containers such as jars, barrels, and tires. Sylvatic yellow fever is an enzootic viral disease transmitted among nonhuman primate hosts by various mosquito vectors. Sylvatic yellow fever usually occurs in forested areas.


By the early 1900s, Aedes aegypti was found in the Untied States and every other country in the Western Hemisphere except Canada. Aedes aegypti is still found in Florida. Since viremic humans are the source of infection for yellow fever transmitted by Aedes aeypti, it is possible that infected travelers returning from abroad could cause an outbreak of yellow fever in the United States. Aedes albopictus, the Asian “tiger mosquito,” is also found in the United States and it is a competent laboratory vector of the yellow fever virus. However, there is no evidence that Aedes albopictus has served as a vector of any cases of any human diseases in the United States. The last documented Aedes aegypti-borne yellow fever epidemic in the Western hemisphere occurred in Trinidad in 1954. The last reported case of yellow fever in Florida occurred in 1918.

For more information please visit the Florida Department of Health website.