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Powassan Virus Disease


Powassan virus (POWV) is named for Powassan, Ontario, where it was first discovered in 1958. It is a rare arboviral infection transmitted by the bite of an infected tick. POWV has been found in Ixodes scapularis, Ixodes cookei, and Dermacentor andersoni species of ticks. Known hosts include humans, woodchucks, foxes, raccoons, skunks, and other small mammals. Though more than 130 arboviruses are known to cause human disease, Powassan virus is the only arbovirus in North America transmitted by ticks (most are transmitted by mosquitoes).

POWV disease can cause encephalitis (inflammation of the brain) and meningitis (inflammation of the membranes that surround the brain and spinal cord). Signs and symptoms of POWV disease include but are not limited to fever, headaches, vomiting, weakness, confusion, loss of coordination, speech difficulties, and memory loss. Infection with POWV disease has been fatal in many reported cases.

The Midwest and northeastern parts of the United States account for the majority of POWV disease cases. From 2001-2009, there were 20 documented cases of POWV disease in Maine, Michigan, Minnesota, New York, Virginia, and Wisconsin. In 2011, Pennsylvania reported its first case of POWV disease. Most cases have illness onset from May to September, when tick vectors responsible for transmission are most active. No cases have ever been reported in West Virginia.

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