Powassan Information for Health Professionals - Minnesota Dept. of Health

Powassan (POW) Virus Information for Health Professionals

Powassan (POW) virus is a tick-transmitted flavivirus, that includes a strain (lineage II or “deer tick virus”) that is transmitted by 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.

On this page:
Clinical Presentation/Diagnosis

April 10, 2015: Minnesota Laboratory System (MLS) Update
Powassan and Arbovirus Testing for the 2015 Season

May 20, 2014: Tick-borne Disease Health Alert
Tick-borne Disease Risk High

June 29, 2011: Tick-borne Disease Health Alert
Minnesota Records First Death from Tick-Borne Powassan Virus


Clinical Presentation/Diagnosis

  • Medical providers should consider POW virus infection in patients with encephalitis or meningitis of probable unknown etiology that occurs during the tick-borne disease transmission season (May to October).
  • Signs and symptoms of POW 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 POW virus infection.
  • 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 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 and other tick-borne diseases. Call 651-201-5414 for a clinical consultation.


Updated Thursday, August 06, 2015 at 11:56AM