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Eastern Equine Encephalitis

Eastern equine encephalitis is a virus (EEEV) that is transmitted to humans by an infected mosquito. Mosquitoes that can vector EEEV to humans include some Aedes, Coquillettidia, and Culex species. The avian hosts (birds) that facilitate the lifecycle of this virus live in fresh-water hardwood swamps. Because this habitat can be the home to birds carrying EEEV, areas near freshwater hardwood swamps are more likely to see human cases of EEEV. In the U.S., cases have most commonly been seen in Florida, Georgia, Massachusetts, and New Jersey. The CDC reports that there are on average 11 cases in the U.S. each year. Six human cases of EEEV have been reported in Alabama since 2008.

Horses can also be infected by EEEV, and some cases can be fatal. Risk for humans around an infected horse is low because humans cannot be infected with EEEV from an infected horse. Vaccines do exist for horses (not for humans).

About Eastern Equine Encephalitis Infection

  • EEEV is not spread from person to person.
  • Risk of infection increases for humans that live or visit woodland habitats and people who work outside/participate in outdoor recreational activities outside.
  • Symptoms of severe EEEV are: sudden onset of headache, high fever, chills, and vomiting. The illness can progress to disorientation, seizures and coma.
  • The CDC reports that approximately a third of the patients that develop EEEV die. Many that survive have mild to severe brain damage.
  • Symptoms of EEEV develop 4-10 days after the bite of an infected mosquito.
  • Diagnosis involved tests of blood or spinal fluid.


  • There is no vaccination for EEEV.
  • There are no specific antiviral medications for EEEV.
  • Treatment of severe cases may involve hospitalization, respiratory support, and IV fluids.
  • If you or your family member develop the symptoms of EEEV contact your healthcare provider.

Reduce the Risk

Without an effective vaccine for people, the best way to prevent mosquito-borne disease is by preventing mosquito bites. This can be accomplished through community-based programs and by personal protection behaviors, such as:

  • Mosquito-avoidance. Avoid outdoor activities when high virus activity levels have been detected or when mosquitoes are most active.
  • Use of personal insect repellents. Use EPA-registered insect repellents or covering up with long-sleeved shirts and long pants when outside. Proper application of mosquito repellents on exposed skin and proper clothing decreases the risk of being bitten by mosquitoes.
  • Window screens. Keep windows closed and use air conditioning if possible. Use screens on windows and doors and repair holes in screens to keep mosquitoes outdoors
  • Removal of residential mosquito sources. Once a week, empty, cover, or throw out items that hold water, such as tires, buckets, planters, toys, pools, birdbaths, flowerpots, or trash containers.
  • Outdoor and Indoor Spraying. Select and use insect spray products according to the label instructions. Mosquitoes that transmit EEE can fly in from other areas like swamplands, marshlands, flooded wooded areas, and roadside ditches. Your municipality and/or county may also conduct adulticiding (killing adult mosquitoes) and/or larvicinding (killing immature mosquitoes) activities; please contact your local authorities with questions about their mosquito control programs.
  • See Avoid The Bite for more information about preventing mosquito-borne diseases. To learn more about insect repellents, visit this Environmental Protection Agency website: Insect Repellent Information from the EPA.

Related Links

For questions or concerns regarding insect-borne disease in Alabama, see the Contact Us page, or email us at [email protected].

Page last updated: September 18, 2023