About Powassan Virus Disease
Powassan virus is a flavivirus, in the same family as tick-borne encephalitis virus, West Nile virus and dengue. It comes in 2 lineages. Lineage 1, the original Powassan virus, is carried by the groundhog tick and squirrel tick, which rarely bite people. Lineage 2, called deer tick virus, is carried by the blacklegged tick, the same tick that spreads Lyme disease, anaplasmosis and babesiosis, and that is why human cases have been rising as blacklegged ticks spread. Unlike Lyme disease, which usually needs a tick attached for more than a day, Powassan virus can pass in a much shorter attachment.
Many infections cause no symptoms. When illness develops, it starts with fever, headache, vomiting and weakness and can progress to encephalitis (brain inflammation) or meningitis. The CDC reports that about 10% of neuroinvasive cases are fatal and about half of survivors have long-lasting neurological deficits such as headaches, muscle weakness, focal paralysis or thinking problems. Treatment is supportive, meaning hospital care for breathing, fluids and brain swelling; antibiotics do nothing against a virus and there is no antiviral drug or vaccine.
Diagnosis relies on antibody tests of blood or spinal fluid, with a positive result confirmed by a specialized neutralizing antibody test at a state public health lab or the CDC, because Powassan antibodies cross-react with other flaviviruses. Testing goes through the state health department. Columbia University's Lyme and Tick-Borne Diseases Research Center, Johns Hopkins and the Global Lyme Alliance all list Powassan among the infections to consider in someone with a tick bite and neurological symptoms.
Common Symptoms of Powassan Virus Disease
Recognizing the signs of Powassan Virus Disease early can lead to faster diagnosis and better outcomes. Symptoms may vary in severity from person to person. If you or a loved one are experiencing any of the following, consider speaking with a specialist.
- No symptoms at all in many infected people
- Fever, headache, vomiting and weakness, 1 to 5 weeks after a bite
- Confusion, loss of coordination and trouble speaking as the brain becomes involved
- Seizures
- Weakness or paralysis of part of the body
- Long-term headaches, muscle weakness or memory problems in about half of severe-illness survivors
Who Powassan Virus Disease Affects
Anyone bitten by an infected tick in an area where the virus circulates. Older adults, children including infants, and people with weakened immune systems are at highest risk of severe disease. The virus has also spread, rarely, through blood transfusion, and the CDC asks people who had it not to donate blood or bone marrow for 120 days.
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Diagnosis and Testing
Tick-borne viral infection, diagnosed by antibody tests confirmed at a public health lab; not genetic.
Trusted Powassan Virus Disease Resources
Reputable organizations and medical references for learning more about Powassan Virus Disease, including disease registries, foundation resources, and clinical guidelines.