Powassan virus is spread to people by the bite of an infected tick. Although considered rare, the number of reported cases of people sick from Powassan virus has increased in recent years. Most cases in the United States occur in the northeast and Great Lakes regions primarily in the late spring, early summer, and mid-fall when ticks are most active. There are no vaccines to prevent or medicines to treat Powassan virus infection. People with severe Powassan virus disease often need to be hospitalized to receive support with breathing and swelling in and around the brain. Reduce your risk of infection from Powassan virus by avoiding ticks. Learn to prevent tick bites, prevent ticks on your pets, and prevent ticks in your yard.