Powassan (POW) Virus Statistics
Since 2008, 22 cases (1 fatal) of Powassan (POW) disease have been reported in Minnesota residents. Most of these patients had neuroinvasive disease (12 encephalitis and 8 meningitis) but 2 were non-neuroinvasive POW fever cases. Seventeen (77%) cases have been male, and the median age is 52 years (range, 3 mos. to 75 years). Seven patients (32%) were immunocompromised. With the exception of 2014 and 2015, cases have been reported every year since 2008, with a peak of 11 in 2011 (range, 1 to 11).
Similar to other tickborne diseases, the majority of patients (82%) reported illness onsets between May and August. Four patients (18%) had onset dates in October or November. Cases were exposed to ticks in several north-central Minnesota counties. MDH has also identified POW virus-positive ticks at sites in the six counties that have been investigated to date (Anoka, Cass, Clearwater, Houston, Morrison, and Pine). Thus, the virus appears to be widely distributed in the same wooded parts of the state that are endemic to other pathogens transmitted by blacklegged ticks.
Charts and Graphs
- Reported Cases of Powassan virus disease in Minnesota
by Year, 2008-2015 (PDF)
Graph showing the number of reported cases of Powassan virus disease in Minnesota by year.
Most Powassan (POW) disease cases report likely exposure to blacklegged ticks in the same east-central, north-central, and southeast Minnesota counties where the risk of Lyme disease is greatest.
- High Risk Areas for Tickborne Diseases in Minnesota
A map that shows counties of highest tickborne disease risk in Minnesota.
Annual Summary Statistics
- Powassan Virus Statistics
Maps, charts, tables, and reports from the CDC. Attention: Non-MDH link