Powassan Virus Infections: A Systematic Review of Published Cases

Powassan virus is an emerging neurotropic arbovirus transmitted by the tick Ixodes scapularis. This systematic review was conducted to aggregate data on its clinical manifestations, diagnostic findings, and complications.

PubMed was searched until August 2023 using the term "Powassan", to identify all published cases of Powassan virus infections, as per PRISMA guidelines.

Among the 380 abstracts identified, 45 studies describing 84 cases (70 adult, 14 pediatric) were included. Cases were reported from the USA and Canada. Complications included paralysis in 44.1% of adult and 42.6% of pediatric cases, cognitive deficits in 33.3% of adult and 25% of pediatric cases, while the mortality rate was 19.1% and 7.1% in the adult and pediatric populations, respectively. Correlation analysis revealed an association between mortality and age (r = 0.264, p = 0.029), development of paralysis (r = 0.252, p = 0.041), or respiratory distress or failure (r = 0.328, p = 0.006). Factors associated with persistent neurological deficits were development of ataxia (r = 0.383, p = 0.006), paralysis (r = 0.278, p = 0.048), speech disorder (r = 0.319, p = 0.022), and cranial nerve involvement (r = 0.322, p = 0.017). Other significant correlations included those between speech disorders and ataxia (r = 0.526, p < 0.001), and between paralysis and respiratory distress or failure (r = 0.349, p = 0.003).

Powassan virus infections have significant morbidity and mortality and should be suspected in cases of encephalitis and possible tick exposure. PROSPERO registration number: CRD42023395991.