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.

Since 2008, 22 cases (1 fatal) have been identified in Minnesota residents. Most patients had neuroinvasive disease (12 encephalitis and 8 meningitis) but 2 were non-neuroinvasive POW fever cases. Seventeen (77%) cases were male. The virus appears to be widely distributed in the same wooded parts of the state that are endemic to other tick-borne diseases transmitted by I. scapularis.

On this page:
Clinical Presentation/Diagnosis
Reporting
Treatment
Guidelines

Powassan disease

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.

Most patients had neuroinvasive disease (12 encephalitis and 8 meningitis) but 2 were non-neuroinvasive POW fever cases. Seventeenn (77%) cases were male. The virus appears to be widely distributed in the same wooded parts of the state that are endemic to other tick-borne diseases transmitted by I. scapularis.

June 12, 2014: Minnesota Laboratory System (MLS) Update
Powassan and Arbovirus Testing for the 2014 Season

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%.

Treatment

  • 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

  • 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.

Guidelines

Updated Friday, August 29, 2014 at 09:30AM