Powassan Virus: Symptoms, Transmission, and Neurologic Risks
Powassan virus can be transmitted within minutes of tick attachment
The infection may cause encephalitis and long-term neurologic complications
Powassan virus shares the same deer tick vector as Lyme disease
In their article Underrecognized Tickborne Illnesses: Borrelia Miyamotoi and Powassan Virus, Della-Giustina et al. explain what Powassan virus is and why it is raising concerns.1
“We chose to review the Powassan virus because it only requires 15 min. of tick attachment for transmission, and the sequelae of the neurologic disease are devastating, in addition to a 10% mortality rate,” the authors write.1
What Is Powassan Virus?
The Powassan virus (POW) is a tick-borne flavivirus related to dengue, yellow fever, West Nile encephalitis, and tick-borne encephalitis viruses.2
“Flaviviruses are a group of single stranded RNA viruses that cause severe endemic infection and epidemics on a global scale,” the authors explain.2
Other tick-borne viruses identified in recent years include the Heartland virus and Bourbon virus.
POW is genetically very similar to deer tick virus, and the clinical presentations are considered identical.
How Was Powassan Virus Discovered?
Powassan virus was first identified in the brain tissue of a young child who died from severe encephalitis.
“Powassan virus is named for the Ontario, Canada, town where it was first isolated from the brain of a 5-year-old boy who died of severe encephalitis in 1958,” the authors write.1
Where Has Powassan Virus Been Reported?
The second known case was reported in New Jersey in 1970 and another in eastern Russia in 1978.
Since then, cases have been reported in a growing number of U.S. states.
In 2019, cases were reported in Connecticut, Indiana, Massachusetts, Maine, Minnesota, North Carolina, North Dakota, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, and Wisconsin.
How Is Powassan Virus Transmitted?
Powassan virus is transmitted by Ixodes scapularis ticks, also known as deer ticks or blacklegged ticks.
These same ticks can also transmit Borrelia burgdorferi, the bacterium responsible for Lyme disease.
“Although many flaviviruses have mosquitos as competent vectors, there is no evidence of human POW virus disease transmitted by mosquitos,” the authors point out.1
How Fast Can Powassan Virus Be Transmitted?
Very rapidly.
“Transmission in mice has been shown to occur within 15 min. of I. scapularis attachment,” the authors explain.1
This differs from many bacterial tick-borne illnesses because the virus is already present in the salivary glands of the tick rather than primarily in the midgut.
What Are the Symptoms of Powassan Virus?
Many individuals infected with Powassan virus never develop clinically significant illness.1
However, severe neurologic disease can occur.
The authors describe symptoms including:
- disorientation
- headache
- neck stiffness
- high fever
- ocular palsies
- motor weakness
- convulsions
- encephalitis
Powassan encephalitis may also mimic herpes simplex encephalitis.1
Can Powassan Virus Cause Long-Term Neurologic Problems?
Yes.
“Approximately 50% of cases result in lasting hemiplegia, memory problems, and muscle wasting,” the authors explain.1
“Ten percent of cases are fatal.”1
Are There Tests for Powassan Virus?
PCR testing may only be positive during early infection.
“IgG by enzyme-linked immunosorbent assay is the mainstay of diagnosis, but confirmation requires specialized testing,” the authors explain.1
Why Are Co-Infections Important?
Treatable tick-borne co-infections may occur alongside Powassan virus infection.
The authors describe a patient with Powassan encephalitis, Lyme carditis, and Babesia co-infection.
Yoon and colleagues described the case of a 17-year-old young man who died waiting for a Powassan virus test.3
He was not treated for Lyme disease co-infection. Autopsy findings later identified Borrelia spirochetes in his heart and liver, with PCR evidence of spirochetes in the brain and lungs.3
For a broader overview, visit our Lyme Coinfections hub.
Is There Treatment for Powassan Virus?
There is currently no specific antiviral treatment for Powassan virus infection.
Treatment is supportive and may include hospitalization, respiratory support, hydration, and management of neurologic complications.
Frequently Asked Questions
What is Powassan virus?
Powassan virus is a rare tick-borne flavivirus that can cause encephalitis and serious neurologic disease.
How quickly can Powassan virus be transmitted?
Experimental models suggest transmission may occur within 15 minutes of tick attachment.
What ticks carry Powassan virus?
Powassan virus is transmitted primarily by Ixodes scapularis ticks, also known as deer ticks.
Can Powassan virus cause long-term problems?
Yes. Some patients develop persistent neurologic deficits including memory problems, weakness, and muscle wasting.
Is Powassan virus deadly?
Yes. Severe Powassan encephalitis can be fatal in approximately 10% of reported cases.
Is there treatment for Powassan virus?
There is currently no specific antiviral therapy for Powassan virus infection. Treatment is supportive.
Clinical Takeaway
Powassan virus is a rare but potentially devastating tick-borne infection capable of causing encephalitis, permanent neurologic injury, and death.
Unlike Lyme disease, transmission may occur within minutes of tick attachment.
Clinicians should consider Powassan virus in patients presenting with encephalitis, severe neurologic symptoms, or possible deer tick exposure.
Related Articles
These related articles explore Powassan virus, co-infections, tick-borne neurologic disease, and severe deer tick-associated illnesses.
Powassan Virus in Children
Maine Woman Dies From Deer Tick Virus
Powassan Virus Infection Causes Polio-Like Illness
Prevention of Lyme Disease
Neurologic Lyme Disease
References
- Della-Giustina D, Duke C, Goldflam K. Underrecognized Tickborne Illnesses: Borrelia Miyamotoi and Powassan Virus. Wilderness Environ Med. 2021;32(2):240-246.
- Chong HY, Leow CY, Abdul Majeed AB, Leow CH. Flavivirus infection-A review of immunopathogenesis, immunological response, and immunodiagnosis. Virus Res. 2019;274:197770.
- Yoon EC, Vail E, Kleinman G, et al. Lyme disease: a case report of a 17-year-old male with fatal Lyme carditis. Cardiovasc Pathol. 2015 Sep-Oct;24(5):317-321.
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
