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Human Powassan (POW) virus infections have been recognized in the United States, Canada, and Russia. In the United States, cases of POW virus disease have been reported primarily from northeastern states and the Great Lakes region. These cases occur primarily in the late spring, early summer, and mid-fall when ticks are most active.

POW virus disease is a nationally notifiable condition.  To ensure standardization of reporting across the country, CDC recommends that the national surveillance case definition be consistently applied by all state health departments.  POW virus disease cases are rare but the reported number of cases have increased in recent years.

All residents of and visitors to areas where POW virus activity has been identified are at risk of infection. People who engage in outdoor work and recreational activities in endemic areas are at increased risk of infection.

Powassan virus neuroinvasive disease cases reported by year, 2010–2019

Graph showing Powassan virus neuroinvasive disease cases reported by year. See table below.

Source: ArboNET, Arboviral Diseases Branch, Centers for Disease Control and Prevention

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Powassan virus neuroinvasive disease cases reported by year, 2010–2019
Year Number of Reported Cases
2010 8
2011 12
2012 7
2013 12
2014 7
2015 6
2016 21
2017 33
2018 21
2019 39

Powassan virus neuroinvasive disease cases reported by state of residence, 2010–2019

Map of the United States showing Powassan virus neuroinvasive disease cases reported by state of residence. See table below.

Source: ArboNET, Arboviral Diseases Branch, Centers for Disease Control and Prevention

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Powassan virus neuroinvasive disease cases reported by state of residence, 2008–2017
State Number of Reported Cases
Connecticut 8
Indiana 1
Maine 8
Massachusetts 31
Minnesota 38
New Hampshire 5
New Jersey 12
New York 20
North Carolina 1
North Dakota 2
Pennsylvania 6
Rhode Island 4
Wisconsin 30

Powassan virus neuroinvasive disease average annual incidence by county of residence, 2010–2019

 

Map of the continental United States showing the distribution of Powassan virus neuroinvasive disease (encephalitis and/or meningitis) average annual incidence by county of residence from 2008 through 2017. Counties are shaded according to incidences ranging from less than 0.20, 0.20 to 0.49, and greater than 0.50 per 100,000 population. Shaded counties are primary in Minnesota, Wisconsin, and New England states.

Source: ArboNET, Arboviral Diseases Branch, Centers for Disease Control and Prevention

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This map shows the distribution of Powassan virus neuroinvasive disease (encephalitis and/or meningitis) average annual incidence by county of residence from 2010 through 2019. Counties are shaded according to incidences ranging from less than 0.20, 0.20 to 0.49, and greater than 0.50 per 100,000 population. Shaded counties are primarily in Minnesota, Wisconsin, and New England states. Top of Page

Additional Maps, Charts, and Tables

Powassan virus disease cases and deaths reported to CDC by year and clinical presentation, 2010-2019

Powassan virus disease cases and deaths reported to CDC by year and clinical presentation, 2009-2018
Neuroinvasive disease Non-neuroinvasive disease Total
Year Cases
No.		 Deaths
No. (%)		 Cases
No.		 Deaths
No. (%)		 Cases
No.		 Deaths
No. (%)
2010  8 0  (0)  0 0  (0)  8 0  (0)
2011 12 1  (8) 4 0  (0) 16 1  (6)
2012 7 0  (0) 0 0  (0) 7 0  (0)
2013 12 2  (17) 3 0  (0) 15 2  (13)
2014 7 0  (0) 1 0  (0) 8 0  (0)
2015 6 1  (17) 1 0  (0) 7 1  (14)
2016 21 3  (14) 1 0  (0) 22 3  (14)
2017 33 2  (6) 1 0  (0) 34 2  (6)
2018 21 3  (14) 0 0  (0) 21 3  (14)
2019 39 9  (23) 4 0  (0) 43 9  (21)
Total  166 21 (12)   15 0  (0)  181 21 (11) 

Source: ArboNET, Arboviral Diseases Branch, Centers for Disease Control and Prevention

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Powassan virus disease cases reported to CDC by state of residence, 2010–2019

Powassan virus disease cases reported to CDC by state of residence, 2008–2017
State 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 Total
Alabama 0 0 0 0 0 0 0 0 0 0 0
Alaska 0 0 0 0 0 0 0 0 0 0 0
Arizona 0 0 0 0 0 0 0 0 0 0 0
Arkansas 0 0 0 0 0 0 0 0 0 0 0
California 0 0 0 0 0 0 0 0 0 0 0
Colorado 0 0 0 0 0 0 0 0 0 0 0
Connecticut 0 0 0 0 0 0 1 0 2 5 8
Delaware 0 0 0 0 0 0 0 0 0 0 0
Dist. of Columbia 0 0 0 0 0 0 0 0 0 0 0
Florida 0 0 0 0 0 0 0 0 0 0 0
Georgia 0 0 0 0 0 0 0 0 0 0 0
Hawaii 0 0 0 0 0 0 0 0 0 0 0
Idaho 0 0 0 0 0 0 0 0 0 0 0
Illinois 0 0 0 0 0 0 0 0 0 0 0
Indiana 0 0 0 0 0 0 0 0 1 0 1
Iowa 0 0 0 0 0 0 0 0 0 0 0
Kansas 0 0 0 0 0 0 0 0 0 0 0
Kentucky 0 0 0 0 0 0 0 0 0 0 0
Louisiana 0 0 0 0 0 0 0 0 0 0 0
Maine 0 0 0 1 0 1 1 3 0 2 8
Maryland 0 0 0 0 0 0 0 0 0 0 0
Massachusetts 0 0 0 1 4 3 5 3 6 9 31
Michigan 0 0 0 0 0 0 0 0 0 0 0
Minnesota 3 11 4 1 0 0 5 7 3 7 41
Mississippi 0 0 0 0 0 0 0 0 0 0 0
Missouri 0 0 0 0 0 0 0 0 0 0 0
Montana 0 0 0 0 0 0 0 0 0 0 0
Nebraska 0 0 0 0 0 0 0 0 0 0 0
Nevada 0 0 0 0 0 0 0 0 0 0 0
New Hampshire 0 0 0 1 0 0 1 1 0 2 5
New Jersey 0 0 0 1 1 1 0 4 1 4 12
New Mexico 0 0 0 0 0 0 0 0 0 0 0
New York 1 0 1 5 1 1 2 6 4 5 26
North Carolina 0 0 0 0 0 0 1 0 0 0 1
North Dakota 0 0 0 0 0 0 0 1 0 1 2
Ohio 0 0 0 0 0 0 0 0 0 0 0
Oklahoma 0 0 0 0 0 0 0 0 0 0 0
Oregon 0 0 0 0 0 0 0 0 0 0 0
Pennsylvania 0 1 0 0 0 0 0 4 1 0 6
Puerto Rico 0 0 0 0 0 0 0 0 0 0 0
Rhode Island 0 0 0 0 0 0 1 2 0 1 4
South Carolina 0 0 0 0 0 0 0 0 0 0 0
South Dakota 0 0 0 0 0 0 0 0 0 0 0
Tennessee 0 0 0 0 0 0 0 0 0 0 0
Texas 0 0 0 0 0 0 0 0 0 0 0
Utah 0 0 0 0 0 0 0 0 0 0 0
Vermont 0 0 0 0 0 0 0 0 0 0 0
Virginia 0 0 0 0 0 0 0 0 0 0 0
Washington 0 0 0 0 0 0 0 0 0 0 0
West Virginia 0 0 0 0 0 0 0 0 0 0 0
Wisconsin 4 4 2 5 2 1 5 3 3 7 36
Wyoming 0 0 0 0 0 0 0 0 0 0 0
Total 8 16 7 15 8 7 22 34 21 43 181

Source: ArboNET, Arboviral Diseases Branch, Centers for Disease Control and Prevention

To request data for previous years, please email dvbid2@cdc.gov.

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Page last reviewed: November 17, 2020
Content source: Centers for Disease Control and Prevention, National Center for Emerging and Zoonotic Infectious Diseases (NCEZID),
Division of Vector-Borne Diseases (DVBD)