Eastern Equine Encephalitis

(WPRI) - Here are some of the symptoms and other facts about Eastern Equine Encephalitis from the Centers for Disease Control.

Eastern equine encephalitis (EEE) is a mosquito-borne viral disease. EEE virus (EEEV) occurs in the eastern half of the United States where it causes disease in humans, horses, and some bird species. Because of the high mortality rate, EEE is regarded as one of the most serious mosquito-borne diseases in the United States.

Transmission

• EEEV is transmitted to humans through the bite of an infected mosquito. It generally takes from 3 to 10 days to develop symptoms of EEE after being bitten by an infected mosquito.
• The main EEEV transmission cycle is between birds and mosquitoes.
• Many species of mosquitoes can become infected with EEEV.  Transmission to horses or humans requires mosquito species capable of creating a “bridge” between infected birds and uninfected mammals such as some Aedes, Coquillettidia, and Culex species.
• Horses are susceptible to EEE and some cases are fatal. EEEV infections in horses, however, are not a significant risk factor for human infection because horses are considered to be “dead-end” hosts for the virus (i.e., the amount of EEEV in their bloodstreams is usually insufficient to infect mosquitoes).

Effects of EEE on humans

• Many persons infected with EEEV have no apparent illness. In those persons who do develop illness, symptoms range from mild flu-like illness to EEE (inflammation of the brain), coma and death.
• The mortality rate from EEE is approximately one-third, making it one of the most deadly mosquito-borne diseases in the United States.
• There is no specific treatment for EEE; optimal medical care includes hospitalization and supportive care (for example, expert nursing care, respiratory support, prevention of secondary bacterial infections, and physical therapy, depending on the situation).
• Approximately half of those persons who survive EEE will have mild to severe permanent neurologic damage.

Who is at risk?

• Residents of and visitors to endemic areas(areas with an established presence of the virus)
• People who engage in outdoor work and recreational activities in endemic areas
• Persons over age 50 and younger than age 15 seem to be at greatest risk for developing severe EEE when infected with the virus.