Powassan fever - Altmeyers Encyclopedia

Definition
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Arbovirus transmitted by ticks (Ixodes species). Very rare disease.

Powassan virus, family Flaviviridae. Hosts are woodchucks and squirrels. Transmission by Ixodes species (Ixodes cookei; Ixodes scapularis). Transmission can occur through all stages of ticks. There is no reactivation phase of the virus within the tick, the tick is immediately capable of infection. Transmission of the Powassan virus from the tick to the host animal is possible immediately after the tick has infested the host animal (within max. 15 minutes).
Infection with the Powassan virus is also possible by the consumption of non-pasteurised goat's milk.

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Dermatology

Characteristic but non-pathognomic immunological reaction to toxins of beta-hemolytic group A streptococci....

AK for 1% of the inhabitants in enzootic areas.
Primarily from a child with deadly Encephalitis in Ontario/Canada (1958). In 1970-1978 eight more cases of encephalitis in the upper part of New York State.
According to seroepidemiological studies, the Powassan virus has a focal occurrence tied to geographically narrow regions. So far proven in Russia, USA, Canada.
In Canada and the USA, antibodies against the Powassan virus are detectable in 0.5-4% of the population.

Especially children are affected.

The incubation period is at least 1 week. Afterwards acute high fever up to 40 °C, headache, cramps. Symptoms of meningeal irritation and encephalitis. Mostly signs of a focal lesion are present, with corresponding loss of sensory and motor functions. The virus has been detected in basal ganglia, cortex and cerebellum of deceased patients.
Neurological deficits persist in 30-50% of surviving patients, most commonly hemiplegia.
The clinical course of Powassan encephalitis may mimic that of meningoencephalitis herpetica (HSV encephalitis).