Eastern equine encephalitis (EEE or Triple E) virus is transmitted by the bite of infected mosquitoes. It can cause serious illness in people as well as horses, donkeys, emus and ostriches. Although uncommon in people, Triple E is one of the most severe mosquito-transmitted diseases in both horses and humans in the United States. Approximately a third of people who become ill with Triple E die. Many people who survive Triple E suffer from long term brain damage. Those under age 15 and over age 50 are at greatest risk of developing severe disease. From 2003 to 2020, 12 human cases of Triple E were reported in North Carolina, with infections occurring from July through December.
In North Carolina, Triple E virus is most commonly detected in the eastern part of the state, where the virus is normally passed between wild birds and mosquitoes. The mosquito species that is the main carrier of Triple E spends most of its time in freshwater swamps and almost exclusively bites birds rather than horses and humans.
People can protect themselves from Triple E by preventing mosquito bites. Consistent use of effective mosquito repellents during the months when they are active is important. A second method is mosquito control efforts, especially in areas near freshwater swamps. There is no vaccine to protect humans from Triple E, and no cure once a human is infected. Treatment is limited to managing the symptoms of the disease.
Autumn is also the time of year when most cases of other mosquito borne viral illnesses are reported, such as West Nile virus and La Crosse virus infections. To prevent mosquito-borne illness, NCDHHS’ Division of Public Health encourages people to practice the “3 Ds”:
- Dress – Wear loose, light-colored clothing that covers your skin.
- Defend – When the potential exists for exposure to mosquitoes, repellents containing DEET (N,N-diethyl-meta-toluamide) are recommended. Picaridin and oil of lemon eucalyptus are other repellent options. Learn more about insect repellent options.
- Drainage – Check around your home to rid of standing water, which is where mosquitoes can lay their eggs.
Most people infected with eastern equine encephalitis don’t develop symptoms, but some can come down with fever or swelling of the brain and about one third of people infected die. There have been three cases of eastern equine encephalitis in the U.S. this year, according to the U.S. Centers for Disease Control and Prevention, one each in Massachusetts, New Jersey, and Vermont. The worst year for the disease was 2019, with 38 cases.
If you have specific questions pertaining to Triple E in humans, please contact the Communicable Disease Branch at 919-733-3419.
For questions about Triple E in horses, please consult your veterinarian or the North Carolina Department of Agriculture and Consumer Services, Veterinary Division, at 919-733-7601.
Vaccines don’t protect or prevent. They simply help fight the virus if you get it.