MONDAY, June 29, 2026 (HealthDay News) — A rare but dangerous tick-borne virus called Powassan is appearing more often across the United States, and experts say warmer weather may be helping it spread.
The U.S. Centers for Disease Control and Prevention (CDC) reported seven cases nationwide in 2015. By 2025, that number had climbed to 76, according to The Washington Post.
As of June 16, the CDC had counted seven cases this year — five in Massachusetts and one each in New York and Wisconsin. However, health officials in Maine and Rhode Island each reported an additional case in the past week.
Powassan virus is spread mainly by the deer tick, also called the blacklegged tick, the same tick that carries Lyme disease. It has been recognized largely in the Northeast and Upper Midwest, The Post reported.
One reason experts worry is how fast the virus spreads into the bloodstream. A tick infected with Lyme generally must feed for 16 to 24 hours to pass on the bacteria, but Powassan may transmit in as little as 15 minutes, Dr. Catherine Valentine, a clinical assistant professor of infectious diseases at NYU Grossman School of Medicine in New York City, told The Post.
Most people who catch the virus have no symptoms. Those who do tend to develop a fever and flu-like aches first. In some cases, the virus invades the central nervous system within a few weeks, leading to encephalitis (brain inflammation) or meningitis, Saravanan Thangamani, a professor of microbiology and immunology at SUNY Upstate Medical University in Syracuse, New York, told The Post.
Neurological symptoms can include confusion, slurred speech, loss of coordination, seizures and even paralysis. Because those symptoms build over days rather than suddenly, they can be mistaken for a stroke.
Among people who develop symptoms, up to 15% die, and about half of survivors are left with lasting neurological problems ranging from memory lapses to trouble walking, speaking or eating, The Washington Post reported.
There is no treatment or vaccine. Severe cases are managed with supportive care such as IV fluids and breathing or feeding support, and some doctors prescribe steroids to ease brain swelling, according to The Post. Rehabilitation can help survivors recover.
Experts point to several reasons for the rise, with climate change leading the list. Warmer temperatures have lengthened tick season and pushed cases into March and November, while milder winters may be boosting the deer and rodent populations that ticks feed on, The Post reported.
Better testing may also play a role in detecting more cases.
The best protection is avoiding bites. Experts advise tucking pants into socks, wearing clothing sprayed with the insecticide permethrin (or purchasing special clothing already treated with it) and using a skin repellent registered with the U.S. Environmental Protection Agency (EPA).
Once home, people should toss all clothing worn outside in a hot dryer for 10 minutes to kill hitchhiking ticks. Folks should also check their skin and clothing for ticks after every outdoor outing.
If a tick is attached, grasp it near the head with tweezers and pull it off, then watch for fever for 30 days, Thangamani advised.
"It's rare," he told The Post, "but it actually has a high human health consequence."
More information
Visit the U.S. Centers for Disease Control and Prevention for more information on the Powassan virus.
SOURCE: The Washington Post, June 28, 2026
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