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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. Cases are reported to CDC by state and local health departments using standard case definitions. 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, 2007–2016

Graph showing Powassan virus neuroinvasive disease cases reported by year, 2007-2016. 7 cases reported in 2007, 2 in 2008, 6 in 2009, 8 in 2010, 12 in 2011, 7 in 2012, 12 in 2013, 7 in 2014, 6 in 2015, and 21 in 2016.

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

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Data Table: In the United States, the number of Powassan virus neuroinvasive disease cases reported each year varies. From 2007 through 2016, an average of 9 cases were reported annually (range 2–21).

Powassan virus neuroinvasive disease cases reported by state of residence, 2007–2016

Map of the United States showing From 2007 through 2016, Powassan virus neuroinvasive disease cases have been reported in Connecticut (1), Maine (3), Massachusetts (13), Minnesota (25), New Hampshire (2), New Jersey (3), New York (17), North Carolina (1), Pennsylvania (1), Rhode Island (1), Virginia (1) and Wisconsin (20).

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

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Data table: From 2007 through 2016, Powassan virus neuroinvasive disease cases have been reported in Connecticut (1), Maine (3), Massachusetts (13), Minnesota (25), New Hampshire (2), New Jersey (3), New York (17), North Carolina (1), Pennsylvania (1), Rhode Island (1), Virginia (1) and Wisconsin (20).

Powassan virus neuroinvasive disease average annual incidence by county of residence, 2007–2016

 

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 2007 through 2016. 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 2007 through 2016. 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.

Additional Maps, Charts, and Tables

Powassan virus disease cases and deaths reported to CDC by year and clinical presentation, 2007-2016

Neuroinvasive disease Non-neuroinvasive disease Total
Year Cases
No.		 Deaths
No. (%)		 Cases
No.		 Deaths
No. (%)		 Cases
No.		 Deaths
No. (%)
2007 7 4  (57) 0 0  (0) 7 4  (57)
2008 2 0  (0) 0 0  (0) 2 0  (0)
 2009  6 0  (0)  0  0  (0)  6 0  (0)
 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)
Total  88 11  (13)   10 0  (0)  98 11  (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, 2007–2016

State 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 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 0 0 0 1 1
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 0 0 0
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 0 0 0 1 0 1 1 3
Maryland 0 0 0 0 0 0 0 0 0 0 0
Massachusetts 0 0 0 0 0 0 1 4 3 5 13
Michigan 0 0 0 0 0 0 0 0 0 0 0
Minnesota 0 1 2 3 11 4 1 0 0 5 27
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 0 0 0 1 0 0 1 2
New Jersey 0 0 0 0 0 0 1 1 1 0 3
New Mexico 0 0 0 0 0 0 0 0 0 0 0
New York 6 1 3 1 0 1 5 1 1 2 21
North Carolina 0 0 0 0 0 0 0 0 0 1 1
North Dakota 0 0 0 0 0 0 0 0 0 0 0
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 0 0 0 1 0 0 0 0 0 1
Puerto Rico 0 0 0 0 0 0 0 0 0 0 0
Rhode Island 0 0 0 0 0 0 0 0 0 1 1
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 1 0 0 0 0 0 0 0 1
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 1 0 0 4 4 2 5 2 1 5 24
Wyoming 0 0 0 0 0 0 0 0 0 0 0
Total 7 2 6 8 16 7 15 8 7 22 98

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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