increased recognition of powassan encephalitis in the united states, 1999-2005. | powassan virus (powv) disease is a rare human disease caused by a tick-borne encephalitis group flavivirus maintained in a transmission cycle between ixodes cookei and other ixodid ticks and small and medium-sized mammals. during 1958-1998, only 27 powv disease cases (mostly powassan encephalitis) were reported from eastern canada and the northeastern united states (average, 0.7 cases per year). during 1999-2005, nine cases (described herein) of serologically confirmed powv disease were reported ... | 2008 | 18959500 |