A Rare, Deadly Mosquito Virus Has Emerged in New York

A dangerous mosquito-borne virus has landed in New York. This week, state health commissioner James McDonald declared that the eastern equine encephalitis (EEE) virus has become an imminent public health threat to New Yorkers, following the first case and death from EEE reported in the state in nearly a decade.

EEE only rarely interacts with humans, since we’re not its natural host and the mosquitoes that typically spread it live in freshwater swamps. But when the virus does invade our bodies, it can trigger a severe brain infection that kills up to a third of victims, so its arrival anywhere is concerning.

Late last month, health officials in Massachusetts reported the state’s first case since 2020; soon after, a second case followed, along with a second case in a horse (despite the name, horses are also an incidental host for the virus). The detection of the first case prompted at least one nearby town to enact a voluntary evening curfew on outdoor activities in hopes of limiting people’s exposure to EEE. So far this year, seven states have reported human cases of EEE (all brain infections), with New York being the latest.

The New York case involved a resident in Ulster County, part of the Hudson Valley region. On September 20, the State Health Department confirmed that the person had contracted EEE, the first case in the state seen since 2015. On Monday, Governor Kathy Hochul announced the resident’s death and said the state would take several steps to curtail EEE, starting with McDonald’s declaration.

“Following the first confirmed human case of EEE, my administration took statewide action to help protect communities—and with today’s declaration we’re making more State resources available to local departments to support their public health response. We’ve been informed this patient has passed away from EEE, we extend our sympathies and our hearts go out to their family,” she said in a statement released by the Governor’s office.

These steps will include making mosquito repellent available to park visitors at park offices, visitor centers, and campground offices throughout the state; displaying signs at parks and other outdoor sites educating people about EEE; and further supporting ongoing mosquito spraying efforts through November, when the mosquitoes will likely finally die off in the winter.

So far at least, the number of EEE cases seen in the U.S. this year is in line with the usual trend. But according to McDonald, the mosquitoes that can transmit EEE have been far more active in New York than normal, having been detected in 15 counties (up from the typical two to three). So people should take steps to keep safe from these and other bloodsucking mosquitoes.

“Mosquitoes, once a nuisance, are now a threat. I urge all New Yorkers to prevent mosquito bites by using insect repellents, wearing long-sleeved clothing and removing free-standing water near their homes,” McDonald said in a statement. “Fall is officially here, but mosquitoes will be around until we see multiple nights of below freezing temperatures.”