Powassan Virusdeer tick

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Photo credit: US CDC

About Powassan

Powassan virus disease is a rare, but often serious disease caused by a virus. Powassan (POW) virus belongs to a group of viruses called flaviviruses. These viruses can cause infection of the brain (encephalitis) or the membranes around the brain and spinal cord (meningitis).

Powassan virus spreads to people through the bite of an infected deer tick (Ixodes scapularis) or woodchuck tick (Ixodes cookei). In rare situations, POW can also spread to a person through a blood transfusion.

Maine CDC reported cases of Powassan virus disease in Maine residents nearly every year since 2013.


Many people who become infected with Powassan virus do not have symptoms. For others, symptoms usually begin one week to one month after the bite of an infected tick. Signs and symptoms may include:

  • Fever and chills

    Fever and chills

  • Headache


  • Neck pain

    Neck pain

  • Weakness


  • Confusion


  • Speech difficulties

    Speech difficulties

People with symptoms of Powassan virus disease may also have loss of coordination and seizures. In severe cases, Powassan virus infection can cause swelling of the brain (encephalitis) or swelling of the membranes around the brain and spinal cord (meningitis). For people who experience severe symptoms, about one out of every ten cases ends in death. About half of survivors have permanent brain damage.

See a healthcare provider if you become ill after a tick bite or spending time in areas where ticks commonly live. Be sure to mention a recent tick bite or time spent in tick habitat to your healthcare provider.


Prevent Tick Bites

The best way to prevent Powassan virus disease is to prevent tick bites in the first place. Take these simple steps every day to prevent tick bites:

  • long pants

    Wear light-colored, long-sleeved clothing and pants. Tuck your pants into your socks.

  • bug spray

    Use an EPA-approved bug spray.

  • trail

    Stay in the middle of trails.

  • tick check

    Do daily tick checks and check your pets for ticks.

Protect Your Yard From Ticks

You can make your yard a tick-safe zone:

  1. Keep the lawn mowed.
  2. Keep leaves raked and get rid of leaf piles.
  3. Move wood piles away from the house. Mice like to live here and can bring ticks with them.
  4. Move birdfeeders away from the house, gardens, and yard toys. Deer and mice like birdfeeders and can bring ticks into the yard.
  5. Use crushed stone or woodchips to make a tick-safe barrier around your yard. This should be 3-feet wide to separate the yard from the woods and keep ticks from crossing into the yard.
tick property maintenance

To learn more about tick bite prevention and how to keep ticks out of your yard, visit Tick Frequently Asked Questions.

Resources for Educators

Maine CDC developed vectorborne school curricula for 3rd-8th grade classrooms. The curriculum is aligned with Maine Learning Results. School nurses, teachers, and other youth leaders are encouraged to use this resource in their classrooms.

Reports and Publications

Powassan Surveillance Reports

Maine CDC publishes data on Powassan cases and rates in Maine in Powassan Surveillance Reports.

  • Powassan Surveillance Report (PDF) 2021

Tickborne Disease Data on the Maine Tracking Network

The Maine Tracking Network uses data from case reports, surveys, and tick submissions to help understand the spread of tickborne diseases in Maine. The dashboard includes real-time data, maps, charts, and graphs for anaplasmosis, babesiosis, and Lyme disease.

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