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.

On this page:
Clinical Presentation/Diagnosis
Reporting
Treatment
Guidelines

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%.

Treatment

• 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

• Reporting Arboviral Disease
  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.

Guidelines

• CDC: Tickborne Diseases of the United States: A Reference Manual for Health Care Providers 
  CDC Handbook, designed as a way for health care providers to access information on tickborne diseases and tick identification.