The Powassan virus was first discovered in a young boy in 1958, when the four-year-old developed symptoms medical experts couldn’t explain.
In 2025, 76 Americans were diagnosed with the virus, the highest number on record and up from an average of seven diagnoses per year.
The virus – which is spread by infected woodchuck or deer ticks – has continued to spread more quickly than usual, leaving experts worried.
Most cases are concentrated in the Northeast United States, the Great Lakes region, and Canada.
While transmission is fast, those who contract the Powassan virus may not develop symptoms for up to four weeks after exposure.
According to the CDC, initial symptoms include:
- Fever
- Headache
- Vomiting
- Weakness
Symptoms of severe illness include:
- Confusion
- Loss of coordination
- Difficulty speaking
- Seizures
In some cases, severe illnesses can lead to complications such as encephalitis and meningitis.
There is no treatment for Powassan virus. The CDC recommends that most patients rest, drink plenty of fluids, and take over-the-counter pain medications to relieve some of the symptoms.
People with severe cases of the disease may need to be taken to hospital for support for breathing, staying hydrated, or reducing swelling in the brain.
Source: metro.co.uk