Powassan Virus Disease Information for Health Professionals - Minnesota Dept. of Health

Powassan Virus Disease Information for Health Professionals

Powassan virus is a tickborne flavivirus, that includes a strain (lineage II or "deer tick virus") that is transmitted by blacklegged ticks (Ixodes scapularis). The virus can cause encephalitis or meningitis, and long-term sequelae occur in approximately 50% of patients. Approximately 10-15% of cases are fatal.

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Clinical Presentation/Diagnosis

Clinical Presentation/Diagnosis

  • Medical providers should consider Powassan virus disease in patients with encephalitis or meningitis of probable unknown etiology that occurs during the tickborne disease transmission season (May to October).
  • Signs and symptoms of Powassan encephalitis or meningitis may include:
    • fever
    • headache
    • vomiting
    • weakness
    • confusion
    • loss of coordination
    • speech difficulties
    • memory loss
  • Long-term sequelae are common, and the case-fatality rate in reported cases is approximately 10%.


  • There is no specific treatment available for Powassan virus disease.
  • Care for patients is typically supportive and may include intravenous fluids and respiratory support.


  • Reporting Powassan Virus
    Minnesota Rules Governing Communicable Diseases require health care providers to report confirmed or suspected cases of Powassan virus disease to the Minnesota Department of Health (MDH) within 1 working day.

MDH staff also are available to provide clinical consultation regarding testing and diagnosis of Powassan virus disease and other tickborne diseases. Call 651-201-5414 for a clinical consultation.


Updated Wednesday, 23-Feb-2022 08:20:34 CST