Powassan virus

noun

Po·​was·​san virus pə-ˈwä-sən- 

variants or less commonly Powassan

1

: a flavivirus (species Powassan virus of the genus Flavivirus) that is transmitted to humans by infected ixodid ticks (especially deer ticks) and that causes a sometimes life-threatening illness

The first case, in 2008, involved a child with encephalitis who was found to be infected with the Powassan virus, an arbovirus that is related to West Nile virus.

—Bridget M. Kuehn

2

or Powassan disease or Powassan virus disease : the illness caused by the Powassan virus that is typically marked by fever, headache, weakness, confusion, loss of coordination, seizures, and often encephalitis or meningitis but that may sometimes be asymptomatic

Note: Powassan virus was first reported in the Canadian municipality of Powassan, Ontario in 1958. The illness typically occurs in the northeastern U.S. and Great Lakes region.

Don't just worry about Lyme disease this summer—Powassan virus is also spread by ticks, and doctors say it could be much more dangerous.

—Charlotte Alter

Severe Powassan often needs hospitalization to receive respiratory support, intravenous fluids or medications to reduce swelling in the brain.

—Nina Radcliff

… blacklegged ticks can also transmit anaplasmosis, babesiosis and Powassan disease according to the Centers for Disease Control and Prevention.

—Andy Ouriel

—abbreviation POW, POWV see also Powassan encephalitis

Examples of Powassan virus in a Sentence

Recent Examples on the Web

If your child has a bug bite and shows symptoms of West Nile, La Crosse, Zika, Lyme disease, Rocky Mountain spotted fever, Powassan virus infection or other illnesses spread by mosquitoes or ticks, talk with your pediatrician. —Dr. Andrew Bernstein, Boston Herald, 13 Aug. 2025

These ticks are the main driver of not only Powassan virus, but also Lyme disease, babesiosis, anaplasmosis and borrelia miyamoto. —Melissa Rudy, FOXNews.com, 7 Aug. 2025

While there have been three cases of Powassan virus in Massachusetts this year, this is the first case in Martha’s Vineyard in 20 years, according to the statement. —Cara Lynn Shultz, People.com, 6 Aug. 2025

None of these [tick-borne] pathogens are transmitted very quickly, except for Powassan virus, which can be transmitted in as little as 15 minutes. —Asuka Koda, CNN Money, 5 Aug. 2025

Word History

Etymology

after Powassan, town in Ontario, where an infection with the virus occurred in 1958

First Known Use

1959, in the meaning defined at sense 1

Rhymes for Powassan virus

• adenovirus
• baculovirus
• coronavirus
• enterovirus
• poliovirus
• antivirus
• herpesvirus
• parvovirus
• reovirus
• retrovirus
• rhinovirus
• rotavirus

Medical Definition

Powassan virus

noun

Po·​was·​san virus pə-ˈwä-sən- 

variants also Powassan

1

: a flavivirus (species Powassan virus of the genus Flavivirus) that is transmitted to humans by infected ixodid ticks (especially deer ticks) and that causes a sometimes life-threatening illness

2

or Powassan disease or Powassan virus disease : the illness caused by the Powassan virus that is typically marked by fever, headache, weakness, confusion, loss of coordination, seizures, and often encephalitis or meningitis but that may sometimes be asymptomatic

Note: Powassan virus was first reported in the Canadian municipality of Powassan, Ontario in 1958. The illness typically occurs in the northeastern U.S. and Great Lakes region.

—abbreviation POW, POWV see powassan encephalitis