Corrin et al.
Powassan virus, a scoping review of the global evidence.
Zoonoses Public Health 2018; 1-30, DOI: 10.1111/zph12485
The authors have analyzed 178 publications dealing with Powassan virus (POWV), which is a flavivirus transmitted by ticks (so far four Ixodes species and one Dermacentor species have been identified as vectors). Studies to identify POWV in other vectors – mosquitos, fleas, lice and mites – have failed. The first report of a POWV infection in humans was in 1958 and since then, 147 POWV cases have been reported in humans, all of them in North America. However, POWV has been introduced to Russia by importation of infected mink. There are two distinct linages of POWV, linage 1 known as POWV linage and linage 2, known as deer tick virus (DTV). These two linages are serologically indistinguishable. Both genotypes have been isolated from ticks and are believed to circulate in different enzootic cycles. Various ELISAs and neutralization assays have been developed to analyze sera of infected hosts. POWV diverged from other tick-borne encephalitis viruses 12.3 thousand years ago and is phylogenetically less close to TBE virus than Alkurma virus and Kyanasur virus (see also snapshot week 18 and 22 as well as the TBE Book, chapter 2a). There are several non-human hosts of POWV and pathogenesis studies have been done in a variety of animals, e.g. mice, chicken, hamster, rabbits, cats and monkeys. Typical symptoms of POWV infection in humans are: headache, confusion, generalized weakness and encephalopathy. Following POWV infection, neurological sequelae are not uncommon. Since 2000, there has been an upward trend in the number of human cases reported each year in the USA. In total, the literature about POWV is relatively small compared to other vector-borne diseases. This article is a comprehensive and useful review about POWV.