Powassan Virus Disease: Symptoms & Signs

Medically Reviewed on 7/15/2021

Powassan virus disease is a rare viral infection. Powassan (POW) virus is a Flavivirus, a genus in the family of Arbovirus; it is related to the West Nile virus. The virus is named after Powassan, Ontario, where it was discovered in 1958. Most cases in the U.S. have been reported in the Northeast and Great Lakes areas.

The infection does not always cause symptoms but can cause meningitis and encephalitis. If symptoms and signs do occur, these may vary in severity and can include

Severe infections may cause death. Long-term complications can include

  • recurring headaches,
  • loss of muscle mass and strength, and
  • memory problems.

Cause of Powassan virus disease

Powassan virus spreads via the bite of an infected tick.

Other powassan virus disease symptoms and signs


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Jameson, J. Larry, et al. Harrison's Principles of Internal Medicine, 20th Ed. New York: McGraw-Hill Education, 2018.