Statistics & Maps

Human Powassan virus infections have been recognized in the United States, Canada, and Russia. In the United States, cases of Powassan virus disease (Powassan) 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.

Powassan cases are rare but the reported number of cases have increased in recent years. All residents of and visitors to areas where Powassan 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 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.

Powassan virus neuroinvasive disease cases reported by year, 2011–2020

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
2011 12
2012 7
2013 12
2014 7
2015 6
2016 21
2017 33
2018 21
2019 39
2020 20

Powassan virus neuroinvasive disease cases reported by state of residence, 2011–2020

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 10
Indiana 1
Maine 9
Massachusetts 37
Minnesota 35
New Hampshire 5
New Jersey 13
New York 21
North Carolina 1
North Dakota 2
Pennsylvania 10
Rhode Island 4
Wisconsin 30

Powassan virus neuroinvasive disease average annual incidence by county of residence, 2011–2020

 

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 primarily in Minnesota, Wisconsin, and New England states.

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

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Data Table: This map shows the distribution of Powassan virus neuroinvasive disease (encephalitis and/or meningitis) average annual incidence by county of residence from 2011 through 2020. 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. Top of Page

Additional Maps, Charts, and Tables

Powassan virus disease cases and deaths reported to CDC by year and clinical presentation, 2011-2020

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. (%)
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)
2020 20 1  (5) 1 0  (0) 21 1  (5)
Total  178 22 (12)   16 0  (0)  194 22 (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, 2011–2020

Powassan virus disease cases reported to CDC by state of residence, 2008–2017
State 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 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 1 0 2 5 2 10
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 1 0 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 1 0 1 1 3 0 2 1 9
Maryland 0 0 0 0 0 0 0 0 0 0 0
Massachusetts 0 0 1 4 3 5 3 6 9 7 38
Michigan 0 0 0 0 0 0 0 0 0 0 0
Minnesota 11 4 1 0 0 5 7 3 7 0 38
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 1 0 0 1 1 0 2 0 5
New Jersey 0 0 1 1 1 0 4 1 4 1 13
New Mexico 0 0 0 0 0 0 0 0 0 0 0
New York 0 1 5 1 1 2 6 4 5 2 27
North Carolina 0 0 0 0 0 1 0 0 0 0 1
North Dakota 0 0 0 0 0 0 1 0 1 0 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 1 0 0 0 0 0 4 1 0 4 10
Puerto Rico 0 0 0 0 0 0 0 0 0 0 0
Rhode Island 0 0 0 0 0 1 2 0 1 0 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 2 5 2 1 5 3 3 7 4 36
Wyoming 0 0 0 0 0 0 0 0 0 0 0
Total 16 7 15 8 7 22 34 21 43 21 194

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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