Powassan Virus Encephalitis Contracted During Winter Months
Powassan virus can cause severe neurologic disease
Tick exposure may occur outside typical seasons
Early recognition may affect diagnosis and care
Powassan virus encephalitis symptoms may include confusion, weakness, headaches, speech problems, and severe neurologic complications. Although uncommon, Powassan virus infection can occur outside typical tick seasons, including winter months.
Powassan virus encephalitis is a rare but potentially severe tick-borne infection that can lead to brain inflammation, cognitive problems, and long-term neurologic complications.
In their article “Powassan Encephalitis: A Case Report from New York, USA,” Bazer and colleagues describe a male patient admitted in December with altered mental status, dysarthria, and a left facial droop.¹
The man also had multiple medical problems including a prior right putamen infarct, hepatitis C, hypertension, and substance abuse history.
Clinicians considered tick-borne disease because the patient reported several recent tick bites.
What Are the Symptoms of Powassan Virus Encephalitis?
Powassan virus symptoms vary considerably. Many infected individuals never develop symptoms, while others develop severe neurologic disease.
“The majority of patients who are infected with Powassan are asymptomatic. When patients are symptomatic from Powassan virus, they will present with encephalitis and altered sensorium.”
Reported symptoms may include:
- Confusion or altered mental status
- Speech problems
- Facial weakness
- Headaches
- Cognitive dysfunction
- Weakness or neurologic deficits
- Balance problems
- Seizures
Powassan symptoms, Powassan disease symptoms, and Powassan encephalitis symptoms are often used interchangeably when patients search for this rare infection.
The virus can cause serious long-term complications. Roughly 50% of patients may experience persistent neurologic sequelae including headaches, cognitive problems, or focal deficits.
Learn more about neurologic manifestations of tick-borne disease.
How Was This Patient Diagnosed?
A spinal tap revealed pleocytosis and elevated protein levels.
“He was empirically treated for possible meningitis with ceftriaxone and acyclovir,” wrote the authors.
He required intubation for airway protection. His illness was later complicated by recurrent stroke and the need for feeding tube support.
The patient was also evaluated for neuromuscular involvement.
“An Electromyography (EMG) and nerve conduction studies (NCS) showed a generalized axon loss with demyelinating polyradiculopathy. He received 2 courses of intravenous immune globulin because of mild demyelinating features on EMG/NCS,” wrote the authors.
Is There Treatment for Powassan Virus?
There is currently no specific antiviral treatment for Powassan virus infection.
Treatment is generally supportive and may include hospitalization, respiratory support, management of brain swelling, intravenous fluids, and rehabilitation.
Early recognition remains important because severe neurologic complications may develop rapidly.
How Long Does Powassan Virus Last?
Recovery time varies considerably. Some individuals recover completely, while others experience persistent neurologic symptoms including cognitive problems, weakness, headaches, or functional impairment for months or longer.
Can Powassan Virus Be Contracted During Winter?
“Although the peak incidence of transmission of the virus is in the summer and fall when the Ixodes species is most active, this does not exclude transmission in other seasons.”
This case highlights an important point: winter months do not eliminate tick exposure risk.
Patients in endemic areas with unexplained neurologic symptoms may still warrant evaluation for tick-borne infections outside traditional tick season.
Learn more about what Powassan virus is and how it spreads.
Why This Case Matters
Testing confirmed active Powassan virus in cerebrospinal fluid, supporting the diagnosis of Powassan encephalitis.
At discharge, the patient continued to have significant neurologic impairment including global aphasia. The authors noted uncertainty regarding whether these deficits reflected Powassan virus, stroke, or both.
This case highlights why clinicians should maintain suspicion for tick-borne neurologic disease even during colder months.
Frequently Asked Questions
Can Powassan virus occur during winter?
Yes. Although transmission peaks during warmer months, tick exposure and infection may still occur during winter.
What are common Powassan virus symptoms?
Symptoms may include confusion, headaches, cognitive problems, speech difficulties, weakness, seizures, and encephalitis.
How serious is Powassan virus encephalitis?
Powassan virus can cause severe neurologic disease. Long-term complications are common among symptomatic patients.
Is there treatment for Powassan virus?
There is no specific antiviral therapy. Management is generally supportive.
Clinical Takeaway
This case highlights the importance of maintaining suspicion for Powassan virus encephalitis in patients with unexplained neurologic symptoms and possible tick exposure—even outside typical transmission seasons.
Tick-borne illnesses should remain part of the differential diagnosis throughout the year in endemic regions.
Related Articles
What is the Powassan virus?
Can Powassan virus cause encephalitis or neurologic damage?
Fatal Powassan virus infection case report
Powassan virus and polio-like illness
References
- Bazer DA, Orwitz M, Koroneos N, Syritsyna O, Wirkowski E. Powassan Encephalitis: A Case Report from New York, USA. Case Rep Neurol Med. 2022;2022:8630349.
Dr. Daniel Cameron, MD, MPH
Lyme disease clinician with over 30 years of experience and past president of ILADS.
Symptoms • Testing • Coinfections • Recovery • Pediatric • Prevention
