The number of infections caused by the rare but dangerous Powassan virus, transmitted by ticks, has increased in the United States more than tenfold over the past decade — from seven cases in 2015 to 76 in 2025, writes The Washington Post columnist Erica Sloan, citing data from the U.S. Centers for Disease Control and Prevention (CDC).
“Among symptomatic patients, the fatality rate is as high as 15 percent, and half of survivors are left with long-lasting neurological fallout, which can range from ‘I keep forgetting the car keys’ to difficulties with speech, walking and sometimes even eating,” said Catherine Valentine, a clinical associate professor of infectious diseases at the New York University School of Medicine.
The virus is notable for its ability to invade the central nervous system and cause encephalitis or meningitis. Symptoms may include confusion, loss of coordination, seizures, and paralysis.
Unlike Lyme disease, where a tick typically needs to be attached for 16–24 hours to transmit the infection, Powassan virus can enter the human body within just 15 minutes of a tick bite, Valentine warned.
