Cases of the rare but potentially fatal tick-borne Powassan virus in the US have reached a record level in 2025. According to the Centers for Disease Control and Prevention (CDC), 76 Americans have been infected with the virus this year. This is the highest annual total on record for a disease that previously saw an average of 7 to 8 cases per year.
The origin of the Powassan virus dates back to 1958, when 4-year-old Lincoln Byers from Ontario, Canada, died from a mysterious illness. Years later, researchers found a tick carrying the same virus on a dead squirrel. This discovery both explained the cause of the tragic death and signaled a growing public health concern.
Fast transmission risk
The virus is transmitted to humans through the bite of an infected groundhog tick or deer tick. Experts warn that its transmission speed makes it uniquely dangerous.
Dr. Jorge P. Parada, medical advisor to the National Pest Management Association in Chicago, said, "One of its most dangerous aspects is its rapid transmission. Powassan can be transmitted as quickly as 15 minutes after an infected tick bite, while Lyme disease typically requires an attachment period of 36 to 48 hours."
Senior medical analyst Dr. Marc Siegel also confirmed that the virus transmits much faster than Lyme disease. He noted the incubation period for Powassan is one to four weeks.
Symptoms and risks
According to the CDC, early symptoms include fever, headache, vomiting, and weakness. Some infected individuals may show no symptoms at all.
The virus can progress to serious neurological complications such as encephalitis (brain inflammation) and meningitis (inflammation of the spinal cord lining). In severe cases, patients may experience confusion, loss of coordination, difficulty speaking, and seizures.
Approximately 10% of Powassan cases that develop severe neurological disease result in death, and most survivors experience long-term neurological problems.
Currently, there is no specific drug or vaccine to treat or prevent the Powassan virus. Clinical care is limited to supportive treatments such as intravenous fluids and respiratory support.
Experts warn that while anyone can develop severe disease, the highest-risk groups are children, older adults, and individuals with weakened immune systems.
