Powassan Virus

Excerpt

Powassan virus (POW) is an arbovirus within the family of Flaviviruses primarily found in the Northeastern United States, Canada, and Russia. It is a zoonotic infection transmitted to humans by several tick species and is the only member of the tick-borne flaviviruses endemic to North America. It was first recognized as a human pathogen in 1958 in Powassan, Ontario. Researchers recovered the virus on autopsy from the brain tissue of a child who died from encephalitis.

Neurologic manifestations represent the most severe POW virus infection presentation, and the majority of cases that present requiring medical care are characterized by encephalitis or meningoencephalitis. In neurologic involvement cases, the case fatality rate is estimated to be between 10% to 15%. Although neuroinvasive infections remain, relatively rare cases have been increasing across the US and Canada over the past decade. The steady increase in cases is likely due both to increased arboviral testing and surveillance and disease emergence.

Evaluation for POW virus infection should be undertaken in those who present with geographic risk factors and a syndrome consistent with encephalitis or meningoencephalitis.