Key points
- Powassan virus disease (Powassan) is a nationally notifiable condition.
- Cases are reported to CDC by state and territorial health departments using standard case definitions.
About Powassan
Powassan virus infections have been identified in the United States, Canada, and Russia. In the United States, cases of 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 work or participate in recreational activities outdoors in endemic areas are at increased risk.
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.