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Eastern Equine Encephalitis

  • Cynthia M. Johnson, MA
Publication Type:


Eastern Equine Encephalitis



Eastern equine encephalitis (EEE) is a rare infection spread by a mosquito bite. It can be serious and sometimes deadly.

Effect on Encephalitis on the Brain.

Swollen brainhttp://services.epnet.com/getimage.aspx?imageiid=73007300si2094.jpgsi2094.jpgNULLjpgsi2094.jpgNULL\\hgfiler01a\intellect\images\si2094.jpgNULL15NULL2008-11-072663907300_165028Copyright © Nucleus Medical Media, Inc.


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

Risk Factors

EEE is more common in people who are under 15 years of age or over 50 years of age.

Things that raise the risk of EEE are:

  • Being in an area where EEE is present
  • Exposure to mosquitoes
  • Being near freshwater hardwood swamps or marshes
  • Having a weakened immune system
  • Working in a lab where EEE is present


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

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

EEE can lead to a serious swelling of the brain called encephalitis. It can cause changes in behavior and thinking, seizures, and coma.


The doctor will ask about 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.

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


The body will need time to get rid of the virus. Treatment will help to support the body and lower the risk of problems. Hospital care may be needed for severe illness, such as brain swelling.

Treatment may include:

  • IV fluids
  • Medicine to:
    • Control seizures
    • Decrease brain swelling
  • Machines to help with breathing


If there is a risk of EEE in the area:

  • Stay inside at dawn and at dusk when mosquitoes are most active.
  • Take steps to stop mosquitoes from getting into the house, such as by repairing screens on windows and doors.
  • 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.

A vaccine is available to lab workers at risk for EEE.





  • Eastern equine encephalitis. Centers for Disease Control and Prevention website. Available at: https://www.cdc.gov/easternequineencephalitis.
  • Eastern equine encephalitis. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/eastern-equine-encephalitis.
  • Encephalitis: an overview. EBSCO Nursing Reference Center Plus website. Available at: https://www.ebsco.com/health-care/products/nursing-reference-center-plus.
  • Lindsey NP, Staples JE, et al. Eastern equine encephalitis virus in the United States, 2003-2016. Am J Trop Med Hyg. 2018;98(5):1472-1477.
  • Mosquito avoidance. EBSCO DynaMed website. Available at: https://www.dynamed.com/prevention/mosquito-avoidance.


  • David L. Horn, MD, FACP
Last Updated:

This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.