Powassan Virus

Type: Viral

Geography: North America, Russian Far East

Cases Per Year: 5 to 30

Fatality Rate: 10%

First Discovered: 1958 in Canada

Powassan virus is spread to people by the bite of an infected tick. Although rare, the number of reported cases has increased in recent years. Most infections occur in late spring through mid-fall when ticks are most active. There are no vaccines to prevent or medicines to treat Powassan virus disease.

Many people infected with Powassan virus do not have symptoms. For people with symptoms, the incubation period is between 1 week and 1 month. Initial symptoms can include fever, headache, vomiting, and weakness. Powassan virus can case severe disease including encephalitis (infection of the brain) or meningitis (infection of membranes around the brain and spinal cord). Severe disease symptoms include confusion, difficult speaking, loss of coordination, and seizures. Approximately half of the people who survive severe disease have long-term health problems, such as recurring headaches, loss of muscle mass and strength, and memory problems.

Photo: Yellow Fever Virus, a lose relative of Powassan Virus – Electron micrograph.