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Powassan Virus

What Is It, Causes, Treatment, and More

Authors:Ashley Mauldin, MSN, APRN, FNP-BC, CNE,Ian Mannarino, MD, MBA

Editors:Alyssa Haag,Kelsey LaFayette, DNP, ARNP, FNP-C

Illustrator:Jessica Reynolds, MS

Copyeditor:David G. Walker


What is the Powassan virus?

The Powassan virus is a single-stranded RNA virus in the Flaviviridae family and Flavivirus genus that causes Powassan virus disease, which leads to inflammation of the central nervous system. Powassan virus disease is a tick-borne disease, and although rare, most reported cases of the Powassan virus infection occur in Canada and the United States—specifically in the northeastern and Great Lakes regions during the spring, summer, and fall months. 

Tick biting human skin.

What causes Powassan virus disease?

Powassan virus disease is caused by the bite of a tick that has been infected with the Powassan virus. Ticks originally contract the virus by biting an animal, such as a squirrel or mouse, that has Powassan virus disease. Then, when the infected tick bites a human, the tick can transmit the virus to the human. Once the infected tick bites a human, the transmission of the virus occurs very quickly, usually within 15 minutes. 

There are three types of ticks (i.e., Ixodes cookei, Ixodes marxi, and Ixodes scapularis) that can spread the Powassan virus. The tick Ixodes cookei (i.e., groundhog tick) along with Ixodes marxi (i.e., squirrel tick) are not known for biting humans. The tick Ixodes scapularis (i.e., black-legged or deer tick), which are known to bite humans, is primarily responsible for the spread of the Powassan virus as well other tick-borne infections like Lyme disease

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What are the signs and symptoms of Powassan virus disease?

Most individuals infected with the Powassan virus will not experience any signs and symptoms. If symptomatic, however, signs and symptoms may include fever, headache, weakness, and vomiting. The Powassan virus can also cause an infection in the brain and spinal cord, resulting in other neurological symptoms like confusion, loss of coordination, and difficulty speaking

Of note, 1 out of every 10 individuals who have a severe case of the Powassan virus infection die, and about fifty percent of those who survive have long-term health problems. Some survivors have permanent health issues, like memory problems, persistent headaches, and muscle wasting. 

How is Powassan virus disease diagnosed?

Diagnosis of the Powassan virus disease is based on history and clinical presentation. A history of living or traveling to an area where the Powassan virus is present, exposure to a tick bite, and any associated signs and symptoms are all indicators of the viral infection. Other tests used to diagnose Powassan virus disease include laboratory tests that look for the presence of IgM antibodies to the Powassan virus in the blood or spinal fluid. Additionally, other methods used to confirm the diagnosis usually include a plaque neutralization assay to improve specificity

How is powassan virus disease treated?

Treatment of the Powassan virus includes supportive care to help minimize symptoms, including rest; fluids; and medications, like NSAIDS, steroids, and immunoglobulins. Those with severe forms of Powassan virus infection may require hospitalization for more intensive care, like IV fluids for hydration, medications to decrease brain swelling, and assistance with ventilation and breathing. 

Currently there are no vaccines that prevent the Powassan virus, so the best way to reduce the risk of becoming infected is prevention. To prevent tick bites, it is advised to always wear clothing that minimizes exposed skin, like long pants and long-sleeved shirts; avoid tick habitats or areas with lots of vegetation; and use tick repellants when spending time outdoors. 

What are the most important facts to know about the powassan virus?

The Powassan virus is a single-stranded RNA virus in the Flaviviridae family and Flavivirus genus. It is the causative agent of Powassan virus disease and transmitted by the bite of a tick that has been infected with the Powassan virus. Most individuals infected with the Powassan virus will not experience any signs and symptoms; however, some individuals may develop manifestations that include fever, headache, weakness, and vomiting along with CNS inflammation. Diagnosis of Powassan virus disease is based on history, physical examination, and the characteristic signs and symptoms. Treatment of Powassan virus disease includes supportive care. There are currently no vaccines that prevent Powassan virus infection, so the best way to reduce the risk of becoming infected is prevention of tick bites

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Resources for research and reference

Fatmi SS, Zehra R, Carpenter DO. Powassan virus: a new reemerging tick-borne disease. Frontiers in Public Health. 2017;5:342. doi:10.3389/fpubh.2017.00342

Powassan virus. Centers for Disease Control and Prevention. Published June 13, 2023. https://www.cdc.gov/powassan/index.html 

Powassan virus disease. Centers for Disease Control and Prevention. Published August 5, 2022. https://www.cdc.gov/ticks/tickbornediseases/powassan.html

Powassan (POW) virus disease fact sheet. New York State Department of Health. Published July 2023. https://www.health.ny.gov/diseases/communicable/powassan/fact_sheet.htm

Preventing tick bites. Centers for Disease Control and Prevention. Published March 30, 2021. https://www.cdc.gov/lyme/prev/index.html