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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, 2006–2015

Graph showing Powassan virus neuroinvasive disease cases reported by year, 2004–2013. 1 case each for 2004, 2005, and 2006. 7 cases reported in 2007. @ in 2008, 6 in 2009, 8 in 2010, 12 in 2011, 7 in 2012 and 12 in 2013.

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

Downloadable version of above graph [PDF – 1 page]

Data Table: In the United States, the number of Powassan virus neuroinvasive disease cases reported each year varies. From 2006 through 2015, an average of 7 cases were reported annually (range 1–12).

Powassan virus neuroinvasive disease cases reported by state, 2006–2015

Map of the United States showing From 2006 through 2015, POWV neuroinvasive disease cases have been reported in Maine (2), Massachusetts (8), Michigan (1), Minnesota (20), New Hampshire (1), New Jersey (3), New York (16), Pennsylvania (1), Virginia (1), and Wisconsin (16).

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

Downloadable version of above map [PDF – 1 page]

Data table: From 2006 through 2015, Powassan virus neuroinvasive disease cases have been reported in Maine (2), Massachusetts (8), Minnesota (20), New Hampshire (1), New Jersey (3), New York (16), Pennsylvania (1), Virginia (1) and Wisconsin (16).

Powassan virus neuroinvasive disease average annual incidence by county, 2006–2015

  Map of the continental United States showing Powassan virus neuroinvasive disease average annual incidence by county, 2006–2015

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

Downloadable version of above map [PDF – 1 page]

Data Table: This map shows the distribution of Powassan virus neuroinvasive disease (encephalitis and/or meningitis) average annual incidence by county from 2006 through 2015. 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.

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