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Travel health information for people travelling abroad from the UK

Eastern Equine Encephalitis


Eastern Equine Encephalitis (EEE) is a viral infection, transmitted to humans by the bite of an infected mosquito. It is most commonly found in eastern, Gulf and north central United States (US) and adjacent Canada, in parts of central and South America and the Caribbean.

It is particularly found in swampy areas during the summer and early autumn months, when there is high mosquito activity. Salt marsh mosquitoes are one of the main carriers. EEE is often a coastal risk due to the large numbers mosquitoes along the shore line. In the US most cases are reported from the states of Florida, Georgia, Massachusetts, and New Jersey.

The Illness

The virus can cause disease in humans, horses and birds. Human cases of EEE are rare (on average 6 cases each year in the US), due the high death rate it is considered one of the most serious mosquito-borne diseases in the US.

Incubation of the disease is normally between 4-10 days, with high fever followed by all the features of meningitis, including coma and convulsions. Of those individuals who contract the disease approximately 35% may die and those that survive the initial illness, 50% may suffer long-term neurological damage.


There is no specific treatment for EEE. Patients will often require hospitalisation and intensive care support to assist with breathing and circulatory problems.

Recommendations for Travellers

Travellers at highest risk are visitors to endemic areas particularly if engaging in outdoor work or recreational activity. Those aged over 50 years and younger than 15 years seem to be at higher risk of developing severe illness if infected with the virus.

No human vaccine against EEE virus is available. Prevention is mainly mosquito bite avoidance.

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