Massachusetts Mosquito Virus: Eastern Equine Encephalomyelitis Explained

A rare but deadly mosquito-borne disease called Eastern equine encephalomyelitis has prompted nearly a dozen Massachusetts towns to close public parks and restrict outdoor activities at dawn and dusk, when the insects are most active.

A 41-year-old man from Hampstead, New Hampshire, has died from complications from the infection, local health authorities said, and another man in his 80s from Worcester County, Massachusetts, was also hospitalized.

But how worried should we be about this disease?

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“Humanity is afraid of invisible things, and this is something invisible,” said Joseph Vinetz, professor of medicine, anthropology and epidemiology at the Yale School of Medicine, Newsweek.

“It's really rare, but it's a thing. You get this mysterious disease where people basically die from inflammation of the brain, so encephalitis, or recover from it after showing symptoms. It's a bad, bad disease, but it's really rare.

“There are a few cases every year and people get scared, but that may be disproportionate to the actual threat.”

Eastern equine encephalomyelitis, also known as “triple E,” is a viral infection transmitted by mosquitoes. In severe cases, the virus can cause brain inflammation, which can be fatal. According to the U.S. Centers for Disease Control and Prevention (CDC), 30 percent of those infected die, and many go on to have neurological problems.

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However, these figures may not reflect the actual number of infections.

“When you see an actual case, it's kind of the tip of the iceberg of all infections, because most cases go undiagnosed,” Vinetz said. “In most cases, it's either a fever that goes away, or it's not clear if there's an obvious infection.”

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According to the CDC, symptoms of Triple E include fever, headache, vomiting, diarrhea, seizures, behavior changes, and drowsiness.

So far, Oxford, Douglas, Sutton and Webster in Massachusetts have declared that they are at “critical risk” from the Triple E plague and urged residents to avoid outdoor activities during peak biting times.

Until September 30, outdoor activities should end by 6 p.m. In October, until the first heavy frost, this only happened at 5 p.m.

The city of Plymouth, about 40 miles southeast of Boston, is closing outdoor recreation facilities from dusk to dawn daily after a horse was found to be infected with the disease.

But what else can you do to protect yourself from Triple E?

“There is no vaccine or treatment, because who would spend $500 million to develop a vaccine for such a rare disease?” Vinetz said.

“[To protect yourself] You need to avoid mosquito bites, so if you live in southeastern Massachusetts or northern Connecticut, you should put on insect repellent when you sit on your porch at dusk, because that's when mosquitoes like to bite. Insect repellents with DEET are useful.”

The CDC also recommends wearing long-sleeved shirts and pants and treating equipment and clothing with mosquito repellent.

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