Endemic progression of autochthonous West Nile virus infections in Europe.

Arthropod-borne West Nile virus (WNV) infections are highly prevalent under warm climate conditions. Our systematic review summarizes recent evidence on autochthonous human WNV infections in Europe considering increasing temperatures due to climate changes, and focuses on geographic expansion, reported drivers, and implications for One Health surveillance, diagnostics, and blood safety. The analysis of 27 included studies published since 2015 revealed progressive geographic expansion of autochthonous WNV infections including outbreaks, in several regions supported by phylogenetic data consistent with sustained local circulation. In selected integrated surveillance settings, detection of WNV in mosquito pools and birds preceded detection of human infections. Rising temperatures were the most consistently reported meteorological correlate of WNV infection incidence and were associated with earlier seasonal onset and prolonged transmission. Across surveillance and case-series data, West Nile neuroinvasive disease (WNND) was disproportionately reported among older male individuals, and patients with distinct comorbidities. The over-representation of WNND among reported cases was compatible with under-ascertainment of mild and asymptomatic infections. In conclusion, given increasing incidences of WNV infections in Europe due to climate changes, awareness and preparedness are pivotal and should prioritize integrated surveillance, blood donor screening, and confirmatory diagnostics with improved serological discrimination in regions with flaviviral co-circulation.