National Center for Advancing and Translational Sciences Genetic and Rare Diseases Information Center, a program of the National Center for Advancing and Translational Sciences

Eastern equine encephalitis


Other Names:
EEE; Triple E
Categories:
Eastern equine encephalitis (Triple E) is an illness caused by a virus that comes from an infected mosquito bite. Most people who are infected have no symptoms, but some may develop fever, headaches, and vomiting. Symptoms occur within 4-10 days of being infected and most recover in 1-2 weeks. A small number will develop swelling of the brain and severe neurological symptoms that can be permanent. Triple E can also lead to coma and death. This condition is caused by a type of arbovirus and is transmitted by a mosquito which has bitten an infected bird or reptile. Diagnosis is based on the symptoms, specific findings in the blood, and occasionally by an MRI of the brain. There is no specific treatment for Triple E. It is managed by taking care of the symptoms. Prevention includes avoiding mosquito bites and controlling mosquito populations.[1][2][3][4]

Last updated: 4/2/2020
The following list includes the most common signs and symptoms in people with eastern equine encephalitis (Triple E) virus infections. These features may be different from person to person. Some people may have more symptoms than others and symptoms can range from mild to severe. This list also does not include every symptom or feature that has been described in this condition.[1][4]
  • Fever
  • Chills
  • Fatigue
  • Vomiting
  • Focal neurological signs
  • Cranial nerve palsies (weakness or loss of function of a large nerve)
  • Coma
  • Seizures
Most people who are infected with the Triple E virus do not get sick. Some develop flu-like symptoms (fever, chills, vomiting) within 4-10 days after being infected. If the infection reaches the brain it can lead to seizures, coma and sometimes, death. Some people may have brain damage that leads to paralysis, intellectual disability or changes in behavior or personality.[1][4] 
Last updated: 4/2/2020
Eastern equine encephalitis (Triple E) is caused by a type of virus called an arbovirus.  Humans catch this virus through a bite from certain types of mosquitos.[2]
Last updated: 4/2/2020
Eastern equine encephalitis (Triple E) is diagnosed in someone who is sick through tests that look for evidence of the triple E virus in blood, tissue or other body fluids.  Sometimes imaging studies, such as an MRI or CT scan can be helpful.[1][5]   
Last updated: 4/2/2020
There is no specific treatment for eastern equine encephalitis (Triple E) virus. Treatment is based on symptoms. The best way to avoid getting Triple E is to avoid mosquito bites.[1][4] 

Specialists who might be involved in the care of someone with Triple E include:
  • Infectious disease specialist
  • Internal medicine or general practitioner
Last updated: 4/2/2020
From 2003 to 2016, twenty states in the United States reported 121 human cases of eastern equine encephalitis. The most cases were in Florida, New Hampshire and Massachusetts.[4]
Last updated: 4/2/2020

These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

Where to Start

  • You can obtain information on this topic from the Centers for Disease Control and Prevention (CDC). The CDC is recognized as the lead federal agency for developing and applying disease prevention and control, environmental health, and health promotion and education activities designed to improve the health of the people of the United States.

In-Depth Information

  • Medscape Reference provides information on this topic. You may need to register to view the medical textbook, but registration is free.
  • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
  • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.
  • PubMed is a searchable database of medical literature and lists journal articles that discuss Eastern equine encephalitis. Click on the link to view a sample search on this topic.

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  1. Berlin D, Gilani AI, Grewal AK, Fowkes M. Eastern equine encephalitis. Pract Neurol. Oct 2017; 17(5):387-391. https://pubmed.ncbi.nlm.nih.gov/28754695.
  2. Gill CM, Beckham JD, Piquet AL, Tyler KL, Pastula DM. Five emerging neuroinvasive arboviral diseases: Cache Valley, Eastern Equine Encephalitis, Jamestown Canyon, Powassan and Usutu. Aug 2019. Semin Neurol; 39(4):419-427. https://pubmed.ncbi.nlm.nih.gov/31533182.
  3. Heberlein-Larson LA, Tan Y, Stark LM, Cannons AC, Shilts MH, Unnasch TR, Das SR. Complex epidemiological dynamics of eastern equine encephalitis virus in Florida. Am J Trop Med Hyg. May 2019; 100(5):1266-1274. https://pubmed.ncbi.nlm.nih.gov/30860014.
  4. Lindsey NP, Staples JE, Fischer M. Eastern Equine Encephalitis Virus in the United States, 2003-2016. Am J Trop Med Hyg. May, 2018; 98(5):1472-77. https://pubmed.ncbi.nlm.nih.gov/29557336.
  5. Nickerson JP, Kannabiran S, Burbank HN. MRI findings in eastern equine encephalitis: the “parenthesis’ sign. Clinical Imaging. Mar-Apr, 2016; 40(2):222-223. https://pubmed.ncbi.nlm.nih.gov/26995574.