When to suspect it
Consider Powassan virus disease in anyone with an acute febrile or neurologic illness and recent tick exposure in areas where it occurs — mainly Ixodes scapularis, Ix. cookei or Ix. marxi. Consider other causes of encephalitis and aseptic meningitis as appropriate, such as herpes simplex viruses, enteroviruses, West Nile virus, St. Louis encephalitis virus, La Crosse virus and eastern equine encephalitis virus.
The virus can rarely be spread by blood transfusion.
Signs and symptoms
- Incubation: 1 to 5 weeks.
- Infection may cause no symptoms, or a non-specific febrile illness.
- First symptoms can include fever, headache, vomiting and generalized weakness.
- It can progress to encephalitis, meningoencephalitis or aseptic meningitis — neuroinvasive disease, which can be severe. Anyone can develop it, but older adults, children and people who are immunocompromised are at higher risk.
- Encephalitis may bring altered mental status, seizures, speech problems (aphasia, dysarthria), paresis or paralysis, movement disorders and cranial nerve palsies.
Test findings
| Test | Typical finding in Powassan meningitis or encephalitis |
|---|---|
| Cerebrospinal fluid | lymphocytic pleocytosis in most patients — though neutrophils can predominate early; protein normal or mildly raised; glucose normal |
| EEG (encephalitis) | generalized slow-wave activity, which can resemble herpes simplex encephalitis |
| Brain MRI (encephalitis) | hyperintensities in the superficial and deep white matter |
Outcomes
About 10% of neuroinvasive cases are fatal, and about half of survivors have long-lasting neurologic deficits — headaches, muscle weakness, focal paralysis or cognitive difficulties.
Sources
Based on "Clinical Signs and Symptoms of Powassan Virus Disease," Centers for Disease Control and Prevention; a work of the United States government in the public domain. The page's photograph was a stock image and is not reproduced.
许可协议： CC0 1.0（公有领域） · 改编自 www.cdc.gov
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