Tick-borne ‘Powassan Virus’ surges across US as health experts sound alarm

A little-known virus first identified after the unexplained death of a four-year-old Canadian boy in 1958 is now drawing renewed concern as infections climb sharply across the United States.

Named after the Ontario town of Powassan, where it was first identified, the rare tick-borne disease recorded 76 confirmed U.S. cases in 2025—the highest annual figure since surveillance began, according to the Centers for Disease Control and Prevention.

Unlike Lyme disease, Powassan virus can be transmitted remarkably quickly. “One of the most dangerous aspects is its rapid transmission,” said Dr. Jorge P. Parada, noting that infection may occur within just 15 minutes of an infected tick bite, whereas Lyme disease generally requires 36 to 48 hours of attachment. Dr. Marc Siegel added that symptoms may not appear for one to four weeks after exposure.

Early signs include fever, headache, vomiting and weakness, although some people develop no symptoms at all. In severe cases, the virus can trigger inflammation of the brain or surrounding tissues, leading to confusion, seizures, speech difficulties and loss of coordination. Around one in ten patients with serious neurological disease die, while many survivors suffer lasting neurological complications. There is currently no vaccine or targeted antiviral treatment, leaving supportive hospital care as the only option. Health authorities advise taking precautions against tick bites, particularly during the warmer months when tick activity is highest.

Image credit: Marino Linic