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Salem Health: Infectious Diseases & Conditions, 2nd Edition

E

by Diane Stresing,

Eastern equine encephalitis

Category: Diseases and conditions

Anatomy or system affected: Brain, central nervous system

Definition

Eastern equine encephalitis (EEE) is a virus affecting wild birds. It is carried by certain mosquitoes and is occasionally transmitted to horses and, rarely, to humans. EEE affects the brain and central nervous system.

Although EEE is more dangerous to horses than to humans (many people infected with the EEE virus do not have any apparent health problems), in some cases, people infected can become suddenly and seriously ill and may experience severe injury to the nervous system; death sometimes follows.

In areas where EEE is known to be present, one should take extra precaution to avoid mosquitoes and to protect against mosquito bites.

Causes

EEE, an arbovirus, is spread by infected invertebrate animals, mostly blood-sucking (hematophagous) insects. Arboviruses are usually spread by infected mosquitoes. Mosquitoes most often get the EEE virus by biting infected birds, and then spreading the virus to horses and other mammals, including humans.

Risk Factors

Because the only known way for humans to contract EEE is by being bitten by an infected mosquito, the risk factor most commonly associated with EEE is exposure to mosquito bites, or living near or visiting a wetland area or an area known to have incidents of EEE. People age fifteen years and younger and age fifty years and older seem to be more susceptible to the infection.

Symptoms

If a person experiences any of the symptoms for EEE, he or she should not assume it is caused by EEE. These symptoms may be caused by other, less serious health conditions. However, one should consult a doctor if any of the following symptoms are present: fatigue; fever; headache; nausea; restlessness or irritability; difficulty walking or unstableness; confusion, impaired judgment, or an altered mental state; or seizures.

Screening and Diagnosis

A doctor will ask about symptoms and medical history, will perform a physical exam, and may order the following tests: blood tests to check if the virus is present; a spinal tap to remove a small amount of spinal fluid to check for signs of infection; an electroencephalogram (EEG) to measure the brain’s activity; a neurological exam to access reflexes, memory, and other brain function; a magnetic resonance imaging (MRI) scan (a scan that uses radio waves and a powerful magnet to produce detailed computer images); and a computed tomography (CT) scan (a detailed X-ray picture that identifies abnormalities of fine tissue structure).

Treatment and Therapy

There are no drug options to treat the EEE virus in humans, so medical treatment focuses on the symptoms of the infection. Such treatments may include antibiotics for secondary infections; anticonvulsants to treat seizures; a respirator to help with breathing; pain relievers to treat headache, fever, and body aches; corticosteroids to reduce swelling in the brain; and sedatives for restlessness or irritability.

Prevention and Outcomes

To help reduce the chance of getting EEE, one should avoid areas of mosquito activity, if possible, and stay inside when mosquitoes are most active (at dawn and at dusk). When outside, one should wear insect repellent, long pants, and long-sleeved shirts to limit exposure to bites. To help limit mosquito populations in and around the home, one should eliminate the insects’ breeding areas, such as standing water in ponds, bowls for pets, rain barrels, and other containers.

Further Reading

1 

Booss, John, Margaret Esiri, and Margaret M. Esin, eds. Viral Encephalitis in Humans. Washington, D.C.: ASM Press, 2003.

2 

Centers for Disease Control and Prevention. “Eastern Equine Encephalitis Virus (EEEV).” Available at http://www.cdc.gov/easternequineencephalitis.

3 

Marquardt, William C., ed. Biology of Disease Vectors. 2d ed. New York: Academic Press/Elsevier, 2005.

4 

North Carolina Department of Health and Human Services. “Arboviruses: Eastern Equine Encephalitis.” Available at http://www.epi.state.nc.us/epi/arbovirus/eee.html.

5 

Stull, J. W., et al. “Eastern Equine Encephalitis—New Hampshire and Massachusetts, August-September 2005.” Journal of the American Medical Association 296 (2006): 645-646. Available at http://jama.ama-assn.org/cgi/content/full/296/6/645.

Web Sites of Interest

Canadian Cooperative Wildlife Centre

http://www.ccwhc.ca

Centers for Disease Control and Prevention

http://www.cdc.gov/ncidod/dvbid

National Institute of Neurological Disorders and Stroke

http://www.ninds.nih.gov

U.S. Department of Agriculture, Animal and Plant Health Inspection Service

http://www.aphis.usda.gov/animal_health

See also: Arthropod-borne illness and disease; Avian influenza; Birds and infectious disease; Blood-borne illness and disease; Carriers; Cholera; Dengue fever; Encephalitis; Insect-borne illness and disease; Mosquito-borne viral encephalitis; Mosquitoes and infectious disease; Poliomyelitis; Psittacosis; Tropical medicine; Viral infections; Viral meningitis; West Nile virus; Yellow fever; Zoonotic diseases.

Citation Types

Type
Format
MLA 9th
Stresing,, Diane. "E." Salem Health: Infectious Diseases & Conditions, 2nd Edition, edited by H. Bradford Hawley, Salem Press, 2020. Salem Online, online.salempress.com/articleDetails.do?articleName=Infect2e_0183.
APA 7th
Stresing,, D. (2020). E. In H. B. Hawley (Ed.), Salem Health: Infectious Diseases & Conditions, 2nd Edition. Salem Press. online.salempress.com.
CMOS 17th
Stresing,, Diane. "E." Edited by H. Bradford Hawley. Salem Health: Infectious Diseases & Conditions, 2nd Edition. Hackensack: Salem Press, 2020. Accessed September 16, 2025. online.salempress.com.