Eastern Equine Encephalitis Virus (EEEV)

What is Eastern equine encephalitis (EEE)?

Eastern equine is a rare mosquito-borne infection caused by the Eastern equine encephalitis virus. Most cases in the United States occur in the Atlantic and Gulf Coast states although cases have occurred in some Midwestern states.

What are the symptoms of EEE?

It is possible that some people who become infected with EEEV may not develop any symptoms. When symptoms develop they may include chills, fever, headache, vomiting, malaise, muscle aches and joint aches. The illness lasts one to two weeks, and recovery is complete when there is no central nervous system involvement. The illness can then progress into disorientation, seizures or coma. EEE is one of the most severe mosquito-transmitted diseases in the United States.

What is the incubation period for EEEV?

The incubation period for EEEV (the time from infected mosquito bite to onset of illness), ranges from four to 10 days. In the United States, an average of six human cases of EEE are reported annually.

How is EEEV transmitted?

The EEEV is transmitted from mosquitoes to humans. Horses can acquire the virus from mosquitoes and many cases in horses are fatal. The primary transmission cycle takes place in and around swampy areas where human populations tend to be limited. The main route of transmission is between mosquitoes and birds. Transmission to dead-end hosts, human and horse, is a departure from this cycle and there is no known transmission between horse and human.

What is the treatment for EEE?

There is no specific treatment of EEE, treatment of symptoms are the usual management of cases.

How does one avoid getting EEE?

The best way to prevent EEE or any other mosquito-borne illness is to reduce the number of mosquitoes around your home and neighborhood and to take personal precautions to avoid mosquito bites. Here are some suggestions:

  • Avoid being outdoors when mosquitoes are most active, especially between dusk and dawn.

  • When outdoors, wear shoes and socks, long pants and a long-sleeved shirt, and apply insect repellent that includes DEET, picaridin, or oil of lemon eucalyptus according to label instructions. Consult a physician before using repellents on infants.

  • Make sure doors and windows have tight-fitting screens. Repair or replace screens that have tears or other openings. Try to keep doors and windows shut, especially at night.

  • Eliminate all sources of standing water that can support mosquito breeding, including water in birdbaths, ponds, flowerpots, wading pools, old tires and any other receptacles. In communities where there are organized mosquito control programs, contact your municipal government to report areas of stagnant water in roadside ditches, flooded yards and similar locations that may produce mosquitoes.
Updated December 2010

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Illinois Department of Public Health
535 West Jefferson Street
Springfield, Illinois 62761
Phone 217-782-4977
Fax 217-782-3987
TTY 800-547-0466
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