The Powassan virus is a tick-borne encephalitis virus related to the classic TBE flavivirus. This disease had its earliest origins in the town of Powassan, Ontario, found in a young boy who eventually died from it.Powassan virus is transmitted by I.cookei among small mammals in eastern Canada and the United States, where it has been responsible for 20 recognized cases of human disease. Other ticks may transmit the virus in a wider geographic area, and there is some concern that I.scapularis (also called I.dammini ), a competent vector in the laboratory, may become involved as it becomes more prominent in the United States.
Time of Transmission
Patients with Powassan encephalitis—often children—present in May through December after outdoor exposure and an incubation period thought to be ~1 week. Powassan encephalitis is severe, and sequelae are common. The Powassan virus can be transmitted in less than 15 minutes of tick attachment.
The Deer Tick Virus
There is a relatively recently identified genotype of the Powassan virus called the Deer Tick Virus.
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Genomic sequencing of deer tick virus and phylogeny of powassan-related viruses of North America. Am J Trop Med Hyg. 2001 Nov;65(5):671-6. PMID: 11716135