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Eastern Equine Encephalitis



Eastern equine encephalitis (EEE) is an infection spread by a mosquito bite. EEE is rare. It can be serious and in some cases, fatal.

Effect on Encephalitis on the Brain
Swollen brain

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EEE is caused by a virus. It is passed to humans from an infected mosquito.

Risk Factors

The risk of EEE is highest in places where the virus is known to be and there are mosquitoes. The risk is also high is if insect repellent is not used in these areas. Other factors that may increase your chances of EEE include:

  • Being over 50 years old or younger than 15 years old
  • Conditions or treatment that lower bodies ability to fight disease


Most people with EEE do not have symptoms. Those that do may have:

  • Headache
  • Neck stiffness
  • Fever
  • Chills
  • Fatigue
  • Joint and muscle pain
  • Vomiting

EEE can lead to swelling of the brain called encephalitis. This is more serious and life-threatening. It can cause change in behavior and thought process, seizures, and coma.


Your doctor will ask about your symptoms and past health. A physical exam will be done. A sample of blood and fluid around the spine will be tested. This will confirm EEE.

Images of the brain may also be needed. This may be done with:


The body will need time to get rid of the virus. Care may be needed for brain swelling. Treatment will help to support the body and decrease problems. Hospital care may be needed for severe illness. Treatment may include:

  • IV fluids
  • Medicine to control seizures
  • Medicine to decrease brain swelling
  • Machines to help you breathe


Be aware of EEE risk in your area. If there is a risk of EEE:

  • Stay inside at dawn and at dusk. This is when mosquitoes are most active.
  • Repair screens on your windows and doors. Take any other steps needed to stop mosquitoes from getting into your house.
  • When outside:
    • Use mosquito netting at night. Look for netting treated with insecticide.
    • Wear insect repellent. Choose long pants and long-sleeved shirts to limit bites.
  • Clear out possible insect breeding areas. Empty areas of standing water, like pet water bowls, rain barrels, and other containers.

Centers for Disease Control and Prevention

National Institute of Neurological Disorders and Stroke


Alberta Health

Health Canada


Eastern equine encephalitis. Centers for Disease Control and Prevention website. Available at: Updated April 5, 2016. Accessed October 28, 2019.

Eastern equine encephalitis. EBSCO DynaMed website. Available at: Updated October 1, 2019. Accessed October 28, 2019.

Encephalitis: an overview. EBSCO Nursing Reference Center website. Available at: Updated September 29, 2017. Accessed October 28, 2019.

Mosquito avoidance. EBSCO DynaMed website. Available at: Updated July 3, 2019. Accessed October 28, 2019.

Last reviewed October 2019 by EBSCO Medical Review Board David L. Horn, MD, FACP