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Click here to see the USGS map of all reported EEE cases this year.

Eastern Equine Encephalitis (EEE)
EEE is an extremely rare mosquito-borne viral disease which occurs in the eastern half of the United States. It causes disease in humans, horses, and some bird species.

You are far more likely to be hit by lightening than to catch EEE! In the forty year period between 1964 and 2004, there were 220 human cases in the United States.  This means that there is an average of approximately 5 cases per year. In contrast, an average of 90 people die in the United States every year from lightning strikes.  And you have a far greater risk of contracting Lyme disease.  In 2005 alone, there were 2336 cases of Lyme disease in Massachusetts.

Outbreaks of EEE usually occur every 10-20 years in Massachusetts, and typically last two to three years.  The most recent outbreak of EEE in Massachusetts began in 2004 and included 13 cases with six fatalities through 2006.

Click here or call your local board of health to learn if EEE has been found in your area. For more information check the Mass. Dept. of Public Health website.

Symptoms and treatment
The first symptoms of EEE are fever (often 103º to 106ºF), stiff neck, headache, and lack of energy.  These symptoms show up three to ten days after a bite from an infected mosquito.  Inflamation and swelling of the brain, called encephalitis, is the most dangerous and frequent serious complication.  The disease gets worse quickly and some patients may go into a coma with a week.

There is no specific treatment for EEE; optimal medical care includes hospitalization and supportive care (for example, expert nursing care, respiratory support, prevention of secondary bacterial infections, and physical therapy, depending on the situation). The mortality rate from EEE is approximately one-third, and approximately half of those persons who survive EEE will have mild to severe permanent neurologic damage.

How is EEE spread?
EEE is spread by the bite of an infected mosquito.  Mosquitoes become infected when they feed on infected birds.

A mosquito which feeds only on birds (known as Culiseta melanura) and which reproduces in freshwater hardwood swamps, is the first to get infected and spread the disease among birds. Then other species of mosquitoes, (such as Aedes, Coquillettidia, and Culex) feed on the infected birds, and also become infected.

The Mass. Dept. of Public Health carefully monitors EEE in mosquito populations throughout the state to determine if there is a risk. 

Click here to learn more about health risks from EEE and other causes.

Prevent mosquito bites!
Click here to learn how you can protect yourself.




Horses are susceptible to EEE, and some cases are fatal.

Infected horses however, are not a significant risk to humans.

This is because horses are considered to be “dead-end” hosts for the virus, since the amount of EEE in their bloodstreams is usually insufficient to infect mosquitoes.