The United States is experiencing a record number of cases for the Powassan virus, a rare and potentially fatal tick-borne illness that can transmit to humans in as little as 15 minutes.
According to the Centers for Disease Control and Prevention (CDC), 76 Americans were diagnosed with the virus in 2025, marking the highest annual total on record. This figure represents a dramatic increase from the previous average of seven to eight diagnoses per year.
The Powassan virus was first identified in 1958 in a case involving a young boy in Canada, named after the Ontario town where it was discovered. The virus is primarily transmitted to humans through the bite of an infected woodchuck tick or deer tick. Its prevalence typically rises from late spring through mid-fall, coinciding with peak tick populations and increased outdoor activities.
Public health experts emphasize the danger posed by the virus's rapid transmission rate. Unlike Lyme disease, which requires a tick to be attached for 36 to 48 hours for transmission, Powassan can be transmitted in a fraction of that time, according to Dr. Jorge P. Parada, a medical advisor at the National Pest Management Association. While still rare compared to other tick-borne illnesses, Powassan elicits clinical concern due to its speed.
Following infection, the virus has an incubation period of one to four weeks before symptoms may appear. Initial symptoms can include fever, headache, vomiting, and weakness. However, some infected individuals may not exhibit any symptoms. The CDC notes that the virus can progress to severe neurological complications such as encephalitis, an inflammation of the brain, and meningitis, an inflammation of the membranes surrounding the spinal cord.
In severe instances, patients may experience confusion, loss of coordination, difficulty speaking, and seizures. Approximately 10% of Powassan cases that lead to severe neurological disease are fatal, and many survivors are left with long-term neurological deficits.
Currently, there are no specific antiviral medications or vaccines available to treat or prevent the Powassan virus. Clinical care is supportive, involving measures such as intravenous fluids and respiratory support. Experts caution that while anyone can contract a severe form of the illness, children, older adults, and individuals with compromised immune systems are at the highest risk.