Powassan Virus Disease

PUBLISHED: May 5, 2017
Relevant to: Ambulatory Care, Hospitals, Medical Office/Clinic

Recent media reports suggest that Powassan (POW) virus disease may be on the rise. However, at this time the Centers for Disease Control and Prevention (CDC) has not issued any specific warnings or advisories about POW. Given the recent media attention, today’s StayAlert! Notice provides a basic overview of Powassan Virus Disease.

POW is a rare, but often serious disease that is caused by a virus spread by infected ticks. Approximately 75 cases of POW virus disease were reported in the United States over the past 10 years. POW virus is one of a group of arthropod-borne viruses (arboviruses) that can cause encephalitis. Facts to note:

  • Many people who become infected with Powassan (POW) virus do not develop any symptoms.
  • The incubation period (time from tick bite to onset of illness) ranges from about 1 week to 1 month.
  • POW virus can infect the central nervous system and cause encephalitis (inflammation of the brain) and meningitis (inflammation of the membranes that surround the brain and spinal cord).
  • Symptoms can include fever, headache, vomiting, weakness, confusion, loss of coordination, speech difficulties, and seizures.
  • Approximately half of survivors have permanent neurological symptoms, such as recurrent headaches, muscle wasting and memory problems.
  • Approximately 10% of POW virus encephalitis cases are fatal.
  • There are no vaccines or medications to treat or prevent POW virus infection.
  • Persons with severe POW illnesses often need to be hospitalized. Treatment may include respiratory support, intravenous fluids, and medications to reduce swelling in the brain.

Preliminary diagnosis is often based on the patient's clinical features, places and dates of travel (if patient is from a non-endemic country or area), activities, and epidemiologic history of the location where infection occurred. Laboratory diagnosis of arboviral infections is generally accomplished by testing of serum or cerebrospinal fluid (CSF) to detect virus-specific IgM and neutralizing antibodies.

In fatal cases, nucleic acid amplification, histopathology with immunohistochemistry and virus culture of autopsy tissues can also be useful. Only a few state laboratories or other specialized laboratories, including those at CDC, are capable of doing this specialized testing. Instructions for sending diagnostic specimens to the CDC Arbovirus Diagnostic Laboratory can be found at the following site: Instructions for Sending Diagnostic Specimens to the CDC Arbovirus Diagnostic Laboratory.

As stated above, despite recent media reports, at this time there is no specific warning or advisory from the CDC. There was a case report, Notes from the Field: Powassan Virus Disease in an Infant — Connecticut, 2016, published in April 2017 that is available for review. The link to that report is provided below.

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