Tick-borne encephalitis virus

**Definition:** Powassan Virus (POWV) is the only tick-borne flavivirus endemic in North America. POWV human illnesses have been reported in the U.S., Canada and Russia. POWV has genetic variations, including deer tick virus (DTV), which is transmitted by the black-legged tick (aka deer tick), Ixodes scapularis. It has two distinct lineages. POWV lineage I is transmitted by the Ixodes cookei, which is endemic in the Great Lakes region. POWV lineage II is transmitted by Ixodes scapularis, which is endemic in the northeastern U.S. Humans can become infected in 15 to 30 minutes after tick attachment.