Powassan Virus Cases Reach Record High of 76 in 2025 as Tick-Borne Threat Expands Across US
Key Insights
Powassan virus (search) cases in the US surged to a record 76 diagnoses in 2025, up from just one case reported in 2004, according to CDC data.
Unlike Lyme disease (search) requiring 36–48 hours of tick attachment, Powassan can transmit in as little as 15 minutes after an infected tick bite.
Approximately 10% of severe neurological Powassan cases are fatal, and many survivors experience lasting neurological damage.
A rare tick-borne virus that can transmit in as little as 15 minutes has reached an all-time high in the United States, with 76 Americans diagnosed in 2025 — the highest annual total on record, according to the Centers for Disease Control and Prevention (search). The figure marks a dramatic escalation from just one recorded case in 2004 and an historical average of seven to eight diagnoses per year.
The Powassan virus (search), named for the Ontario town near where it was first discovered in 1958, is spread primarily by the deer tick — the same vector that carries Lyme disease (search) — as well as the woodchuck tick. But its transmission dynamics set it apart from more familiar tick-borne illnesses.
"One of the most dangerous aspects is its rapid transmission," said Dr. Jorge P. Parada, a medical advisor at the National Pest Management Association (search) in Chicago. "Powassan can be transmitted in as little as 15 minutes after the infected tick bites, while Lyme disease (search) usually requires a 36- to 48-hour attachment time for transmission."
Dr. Marc Siegel, senior medical analyst for Fox News, confirmed the accelerated transmission timeline and noted that the virus carries an incubation period of one to four weeks before symptoms manifest.
Clinical Presentation and Disease Burden
Most Powassan infections cause no symptoms, but early signs can include fever, headache, vomiting, and weakness. In severe cases, the virus can progress to encephalitis (search) — inflammation of the brain — and meningitis (search), or inflammation of the spinal cord membranes. Patients may experience confusion, loss of coordination, difficulty speaking, and seizures.
Approximately 10% of Powassan cases involving severe neurological disease are fatal, and many survivors experience long-term neurological issues. The CDC defines periods of increased tick activity as "late spring, early summer, and mid-fall."
Geographic Spread and Underreporting Concerns
So far in 2025, the CDC has recorded 15 cases across Massachusetts, New Hampshire, New York, Pennsylvania, and Wisconsin. However, those numbers may represent an underestimate. Nicole Baumgarth, a professor of molecular microbiology and immunology at the Johns Hopkins Bloomberg School of Public Health, noted last year that the virus is still relatively new and presents with non-specific symptoms, meaning doctors may not be testing for it.
The Rhode Island Department of Health reported a Powassan virus (search) case last week, which a resident had contracted in May. The CDC acknowledges that "due to delays in reporting, state, territorial, and local health departments may have more up-to-date information than what is presented here."
No Vaccine, No Specific Treatment
There is currently no vaccine or specific antiviral treatment for Powassan virus (search). Clinical care is limited to supportive therapy, such as intravenous fluids and respiratory support, with treatment focused on alleviating symptoms. Prevention therefore hinges on avoiding tick bites entirely.
Public health experts recommend using insect repellents, wearing long sleeves and pants, avoiding bushy and wooded areas, and performing thorough tick checks after spending time outdoors. The CDC offers additional guidance on protecting against tick bites on its website.