The number of cases of the deadly Powassan virus is growing in the United States.

The number of cases of infection with the rare but dangerous Powassan virus, which is carried by ticks, has increased more than tenfold in the United States over the past ten years, from seven cases in 2015 to 76 in 2025, The Washington Post columnist Eric Sloan wrote on June 28, citing data from the US Centers for Disease Control and Prevention.

"Among patients with symptoms, the mortality rate reaches 15%, and half of the survivors are left with long—term neurological consequences that can range from memory problems to difficulties with speech, walking, and even eating," said Catherine Valentine, clinical associate professor of infectious diseases at New York University School of Medicine.

The peculiarity of the virus is that it is able to enter the central nervous system and cause encephalitis or meningitis. Symptoms may include confusion, loss of coordination, seizures, and paralysis. At the same time, infection occurs very quickly: unlike Lyme disease, for which the tick needs to attach to the skin for 16-24 hours, the Powassan virus can enter the human body as early as 15 minutes after the bite, Valentine warned.

Experts attribute the increase in the number of cases to climate change. Warm and humid weather prolongs the tick activity season: cases of infection are recorded as early as March and last until November. In addition, mild winters contribute to the growth of populations of rodents and deer on which ticks feed, which allows them to spread to new regions, explained Saravanan Tangamani, professor of microbiology and immunology at the State University of New York and director of the Center for the Study of Vector-Borne Diseases.

Currently, there is no cure for the virus, nor a vaccine to prevent it. In severe cases, patients are provided with supportive therapy: intravenous fluids, respiratory support, and feeding assistance. Some doctors prescribe steroids to reduce brain inflammation. Survivors with long-term neurological disorders can benefit from physical and cognitive rehabilitation.

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