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Massachusetts sees 1st human case of Eastern equine encephalitis since 2020. Here's what to know

The rare but serious disease is generally spread to humans through the bite of an infected mosquito.
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A human case of Eastern equine encephalitis was identified in Massachusetts for the first time since 2020. Now the state's public health department is ringing the alarm in multiple communities to protect against the potentially deadly virus.

Last week, the Massachusetts Department of Public Health said a man in his 80s had been exposed to the mosquito-borne virus in Worcester County, marking the first human infection in the state in four years.

The discovery raised risk levels in the towns of Douglas, Oxford, Sutton and Webster to critical. The risk was increased to high in Dudley, Northbridge and Uxbridge. Neighboring communities of Auburn, Charlton, Grafton, Leicester, Mendon, Millbury, Millville, Southbridge and Upton are considered at moderate risk.

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EEE is a rare but serious virus spread to humans by an infected mosquito's bite. Within five to 10 days of the bite, an infected person can see symptoms including high fevers, headache, stiff neck, vomiting, seizures, behavioral changes and fatigue, according to Massachusetts health authorities.

Though there are only a few cases in the U.S. each year, with most in eastern or Gulf Coast states, the CDC says around 30% of people who are infected die, and many survivors have ongoing neurological problems.

In Massachusetts, however, the state says about half of those infected with EEE die, and few people recover completely without disability.

The virus was first identified in the state in 1938. Since then, outbreaks lasting two to three years occurring every 10 to 20 years have produced just over 115 cases, the state says.

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Its most recent outbreak began in 2019, with 12 cases ending in six deaths. Continuing into 2020 — the last year the state saw EEE — there were five more cases, one ending in death.

As there are no vaccines to prevent or medicines to treat EEE, the CDC and the Massachusetts Public Health Department say preventing mosquito bites is the best way to reduce the risk of infection.

Prevention efforts should include using an insect repellent with an EPA-registered ingredient like DEET when going outside, avoid peak mosquito hours from dusk to dawn, wear protective clothing, and mosquito-proofing your home. This means repairing any window screens and draining any standing water where mosquitos lay their eggs.