The rare and potentially fatal Powassan virus has reached record-high case numbers in the United States, according to the Centers for Disease Control and Prevention (CDC). In 2025, 76 Americans were diagnosed with the tick-borne illness, marking the highest annual total on record. Previously, the U.S. averaged just seven to eight diagnoses each year.
The virus, named after the Ontario town near where it was first discovered, was linked to a 1958 case involving a 4-year-old boy in Canada. Researchers later identified the virus in a tick found on a dead squirrel, providing an explanation for the boy's unexplained death.
Powassan is primarily transmitted through the bite of infected woodchuck ticks or deer ticks. Unlike Lyme disease, which typically requires 36 to 48 hours of tick attachment for transmission, Powassan can be transmitted in as little as 15 minutes, making it uniquely dangerous. The virus is most prevalent from late spring through mid-fall, when tick populations peak and outdoor activity increases.
Public health experts warn that the rapid transmission rate of Powassan poses significant clinical concerns. While the virus remains rare compared to Lyme disease, its potential for severe outcomes has raised alarms among medical professionals.
Dr. Jorge P. Parada, a medical advisor at the National Pest Management Association in Chicago, emphasized the virus's rapid transmission as one of its most dangerous aspects. He noted that while Powassan is less common than Lyme disease, its ability to spread quickly after a tick bite warrants heightened awareness and preventive measures.