Eastern Equine Encephalitis

Eastern Equine Encephalitis (EEE) is a mosquito-borne viral disease and, because of the rate of death among infected persons, is regarded as one of the most serious mosquito-borne diseases in the United States.

Occurrence & Severity


EEE occurs in the eastern half of the U.S. and is most commonly detected around swamps in Virginia's coastal plain. Symptoms range from mild flu-like illness to encephalitis, coma, and death. About 35% of people who develop the disease die. It is estimated that 35% of people who survive EEE will have mild to severe neurologic after effects from this disease. Human cases of EEE are somewhat rare. The most recent human case of EEE was reported in 2003. Horses and certain birds like ostriches and emus can become infected with, and die from, EEE virus infection.

Virus Characteristics


The EEE virus is maintained in a cycle between Culiseta melanura mosquitoes and avian hosts in freshwater hardwood swamps. Cs. melanura is not considered to be an important vector of EEE to humans because it feeds almost exclusively on birds. Transmission to humans requires mosquito species capable of creating a "bridge" between infected birds and uninfected mammals such as some Aedes, Coquillettidia, and Culex species.