Font Size:

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. Three 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.

Detect, Test, Report

The best preventive measure for residents living in areas infested with disease vectoring mosquito species is to eliminate the places where the mosquito lays her eggs, primarily artificial containers that hold water.

Items that collect rainwater or to store water (for example, plastic containers, 55-gallon drums, buckets, or used automobile tires) should be covered or properly discarded. Pet and animal watering containers and vases with fresh flowers should be emptied and cleaned (to remove eggs) at least once a week. This will eliminate the mosquito eggs and larvae and reduce the number of mosquitoes present in these areas. For more info on how to control mosquitos around your home see Vector Control.

Using air conditioning or window and door screens reduces the risk of mosquitoes coming indoors. Proper application of mosquito repellents on exposed skin and proper clothing decreases the risk of being bitten by mosquitoes. 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

Page last updated: December 7, 2021