Can Powassan Virus Cause Encephalitis in Children?
Powassan virus can cause severe encephalitis and seizures in children.
Two infants developed encephalitis after apparently brief tick attachment.
A newer pediatric case series documented lasting neurologic complications.
Can Powassan virus cause encephalitis in children? Yes. Although Powassan virus infection is uncommon, it can cause severe inflammation of the brain, seizures, confusion, and lasting neurologic problems in children.
An earlier case report described two infants who developed Powassan virus encephalitis after tick bites. More recently, researchers reported six additional pediatric cases involving children between 14 months and 11 years of age.
Together, these reports highlight the potential severity of Powassan virus infection, the possibility of transmission after relatively brief tick attachment, and the importance of preventing tick exposure.
Two Infants Developed Powassan Virus Encephalitis
The first case involved a 5-month-old infant who was hospitalized after two days of fever and vomiting. Facial twitching progressed to seizures. Approximately two weeks before symptoms began, a tick had been removed from the infant’s forehead. Testing for Powassan virus was positive.
The second case involved a 2-month-old infant who developed fever and listlessness. The child subsequently developed focal seizures involving rhythmic left arm twitching, facial deviation, tongue thrusting, and lip smacking.
A tick had been removed from the infant’s arm approximately two weeks before hospitalization. The parents believed that the father or the family dog may have carried the tick into the house following an outdoor walk.
The tick was not engorged, and the family estimated that it had been attached for less than 24 hours. Because the duration was reconstructed from the circumstances reported by the family, the exact attachment time could not be established.
Powassan virus infection was confirmed through plaque reduction neutralization testing of both serum and cerebrospinal fluid.
Both infants recovered.
READ MORE: Powassan Virus: Does It Always Cause Encephalitis?
Newer Report Describes Six Children With Powassan Encephalitis
A more recent pediatric case series described six children with Powassan virus encephalitis diagnosed in New England between 2018 and 2023. The children ranged in age from 14 months to 11 years.
All six children presented with fever and confusion. Most also developed seizures.
The researchers reported lasting neurologic complications in all six children. These included:
- Seizures
- Movement disorders
- Behavioral problems
- Attention difficulties or ADHD
- Learning problems
- Anxiety
- Sleep disturbances
This was the largest published pediatric case series of Powassan virus encephalitis at the time of publication. It provides additional evidence that Powassan virus is a rare but potentially severe cause of encephalitis in children.
Why Powassan Virus Encephalitis Is Concerning
Powassan virus infection can range from an asymptomatic infection or mild febrile illness to severe neurologic disease. When the virus affects the central nervous system, it may cause meningitis, encephalitis, seizures, weakness, altered mental status, impaired coordination, or difficulty speaking.
Approximately 10% of reported neuroinvasive Powassan virus disease cases are fatal. Among people who survive neuroinvasive disease, about half may experience long-lasting neurologic problems, including headaches, muscle weakness, focal paralysis, or cognitive difficulties.
These outcome estimates apply to patients with severe neuroinvasive disease—not to everyone infected with Powassan virus. Many infections may be asymptomatic or produce only a nonspecific febrile illness.
Can Powassan Virus Be Transmitted Quickly?
Unlike several bacterial tick-borne infections, Powassan virus does not necessarily require prolonged tick attachment before transmission can occur.
Experimental research has demonstrated transmission within minutes of tick attachment. The authors of the two-infant report concluded that the circumstances provided epidemiologic evidence that transmission to a human host may occur within hours.
The precise attachment time in an individual case is often difficult to determine. These cases nevertheless demonstrate why preventing tick attachment is particularly important. Prompt removal remains advisable, but families should not assume that a briefly attached tick eliminates the possibility of Powassan virus exposure.
How Were the Two Infants Exposed to Ticks?
Infants generally have limited direct exposure to wooded or grassy environments. In both cases, the authors believed that ticks were probably carried into the home following outdoor activities.
In the first case, the father had been walking in the woods and had brushed several ticks from his clothing before entering the house. He may nevertheless have unknowingly carried another tick indoors.
In the second case, the father had been walking outside with the family dog. The family believed that either the father or the dog may have carried the tick into the home.
These cases illustrate how an infant or young child can encounter a tick without having been outside in a typical tick habitat.
Preventing Tick Exposure in Infants and Children
Parents and caregivers can take several steps to reduce the risk of tick exposure:
- Wear protective clothing in wooded, brushy, or grassy areas.
- Use an appropriate insect repellent according to its label instructions.
- Consider permethrin-treated clothing and outdoor equipment. Permethrin should not be applied directly to the skin.
- Inspect clothing, equipment, and exposed skin after outdoor activities.
- Repeat tick checks because an unattached tick may continue crawling before selecting a place to feed.
- Shower after returning indoors when possible.
- Inspect pets after outdoor exposure because unattached ticks can be carried indoors on their fur.
- Follow veterinary guidance regarding appropriate tick-prevention products for pets.
How Is Powassan Virus Encephalitis Treated?
There is currently no specific antiviral medication approved to treat Powassan virus infection. Antibiotics do not treat Powassan virus because it is a viral infection.
Children with encephalitis may require hospitalization and supportive care. Depending on the severity of the illness, treatment may include intravenous fluids, respiratory support, seizure management, and measures to reduce complications associated with brain inflammation.
Frequently Asked Questions
What is Powassan virus encephalitis?
Powassan virus encephalitis is inflammation of the brain caused by Powassan virus, a tick-borne flavivirus. Severe illness may include fever, confusion, seizures, weakness, difficulty speaking, or impaired coordination.
What symptoms can Powassan virus cause in children?
Reported symptoms include fever, vomiting, confusion, facial twitching, focal seizures, weakness, and altered behavior. Symptoms vary depending on the severity and location of neurologic involvement.
Can Powassan virus be transmitted after brief tick attachment?
Yes. Experimental studies indicate that Powassan virus can be transmitted within minutes. The two infant cases provide epidemiologic evidence that human transmission may occur within hours, although the exact attachment times could not be confirmed.
Do all Powassan virus infections cause encephalitis?
No. Some infected people have no symptoms, while others develop a nonspecific febrile illness. A smaller proportion develop neuroinvasive disease such as meningitis or encephalitis.
Can children have lasting problems after Powassan encephalitis?
Yes. The newer six-patient pediatric series reported lasting neurologic complications, including seizures, movement disorders, behavioral changes, attention and learning problems, anxiety, and sleep disturbances.
Can children recover from Powassan virus encephalitis?
Recovery is possible, and both infants in the earlier report recovered. However, the degree of recovery varies, and some children may experience lasting neurologic complications.
Can ticks be carried into a home?
Yes. Unattached ticks may be carried indoors on clothing, outdoor equipment, or pets. Family members should check themselves, their clothing, and their pets after outdoor activities.
Clinical Perspective
Powassan virus infection remains uncommon in children, but the available pediatric reports demonstrate that severe neurologic disease can occur in infants and older children.
The original two-infant report highlights the possibility of indirect household exposure when ticks are carried indoors. The newer six-patient series demonstrates that pediatric Powassan virus encephalitis may also lead to persistent seizures, movement disorders, behavioral changes, and learning difficulties.
A recognized tick bite can help clinicians identify a possible exposure. However, tick bites may go unnoticed, particularly when the tick is small or attached in a difficult-to-see location. Powassan virus may therefore be considered among the possible causes of an acute febrile neurologic illness in a child with potential tick exposure in an endemic region.
Clinical Takeaway
Powassan virus can cause encephalitis and seizures in children, including very young infants. Transmission may occur after a relatively brief period of tick attachment, and some children who survive encephalitis experience lasting neurologic complications.
Because no specific antiviral treatment is currently available, prevention remains particularly important. Tick checks, protective clothing, properly used repellents, permethrin-treated clothing and equipment, pet inspection, and awareness of ticks being carried into the home can help reduce exposure.
This article discusses published case reports and is intended for educational purposes. It does not provide medical advice or replace evaluation by a qualified healthcare professional.
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References
- Feder, H. M., Telford, S. R., Goethert, H. K., & Wormser, G. P. (2021). Powassan virus encephalitis following brief attachment of Connecticut deer ticks. Clinical Infectious Diseases, 73(7), e2350–e2354.
- Greenlaw, C., MacRae, R., & Wilson-Murphy, M. (2025). Powassan virus encephalitis in pediatric patients. Journal of Child Neurology, 40(10), 824–831.
- Centers for Disease Control and Prevention. (2025). Clinical signs and symptoms of Powassan virus disease.
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
I would like to see follow up for families to better understand what outcomes can occur for children.
My grandson is the first case discussed in this article. He is now 6 years old and there is no guidance for possible complications, though there are some that were not discovered until recently.
Thanks for reminding us of the need for further research.
Thanks for sharing. I have not seen information on possible complications. I am concerned that any subsequent symptoms may be related to a treatable tick borne illness.