Powassan virus
| Powassan virus | |
|---|---|
| Virus classification | |
| Group: | Group IV ((+)ssRNA) |
| Order: | Unassigned |
| Family: | Flaviviridae |
| Genus: | Flavivirus |
| Species: | Powassan virus |
Powassan virus is a flavivirus transmitted by ticks. The disease it causes is named after the town of Powassan, Ontario, where it was identified in a young boy who eventually died from it.
The Powassan Virus (POWV) is normally found in the warm climate across Eurasia where it is part of the TBE-complex. The disease also exists in North America and can be transmitted with bites from the following species of Ixodes ticks: Ixodes cookei, Ix. scapularis, Ix. marxi and Ix. spinipalpus. The ticks Dermacentor andersonii and Dermacentor variabilis are also vectors of the POWV. There are a total of 6 known species of tick that act as vectors, with Ixodes cookei being the predominant species in Canada and the Northeastern United States and Ix. scapularis as a significant vector in Minnesota and Wisconsin. There are rare cases in which Ix. cookei attaches to humans, and as a result the case-patients with POWV have been mostly confirmed as having the strain of POWV, the Deer tick virus (DTV). The Deer Tick Virus plays a vital role in maintaining the POWV and is vectored by Ix. scapularis.Ix. scapularis is an important vector of the enzootic transmission cycle of the Deer Tick Virus.Ix. scapularis is also a primary vector for the agent of Lyme disease because they are a generalist feeder and readily bite humans. The Powassan virus is transmitted by ticks among small mammals in eastern Canada and the United States, where it has been responsible for 49 deaths in the U.S. between 2000–2011. In North America, the Powassan Virus has been noted as the only tick-borne Flavivirus with human pathogenicity so far.
The Powassan virus is rarely diagnosed as a cause of encephalitis; however, when it is, Powassan encephalitis is severe, and neurologic sequelae are common. Powassan encephalitis has symptoms that are compatible with Acute disseminated encephalomyelitis, oftentimes making it difficult to diagnose. Powassan virus encephalitis is a challenge to diagnose because there are only a few laboratories that offer testing, the most effective being serologic testing. There are currently no medications or vaccines to treat or prevent the POWV. Victims of the Powassan virus generally show first symptoms after 1–3 weeks. The initial symptoms for the POWV include: fever, headache, nausea, occasional confusion, and weakness. With severe Powassan illnesses the victims should be hospitalized because the symptoms do worsen. If not treated symptoms could extend to meningoencephalitis, which may include: seizures, aphasia, cranial nerve palsies, paresis and altered mental status. Currently the best ways to treat POWV illnesses include: medications to reduce brain swelling, respiratory support and intravenous fluids. 10% of the POWV encephalitis cases are fatal and half of the survivors have permanent symptoms that affect their brain.
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Wikipedia