Outbreak of autochthonous West Nile virus infection in Lazio region, Italy, July to August 2025: preliminary investigation

In July-18 August 2025, 171 autochthonous cases with West Nile virus (WNV) infection were confirmed in Lazio, Italy: four asymptomatic blood donors, 110 with WNV fever, 57 with neuroinvasive syndrome and nine deaths. WNV lineage 2 was detected in two neuroinvasive cases. Infection with WNV was confirmed in 28 horses, five crows and a <i>Culex pipiens</i> pool. We present the preliminary epidemiological and phylogenetic analysis of the outbreak and the public health measures taken within a One Health approach.