Descriptive Epidemiological Analysis of West Nile Virus Human Infections in Italy: A Surveillance-based Study (2018–2023)

West Nile virus (WNV) is a re-emerging mosquito-borne RNA virus of the Flaviviridae family that continues to pose a significant public health threat. It is maintained in nature through a transmission cycle between wild birds, the main hosts, and vector mosquitoes, primarily Culex spp. In Italy, WNV infections have been reported since 2008, with seasonal outbreaks occurring almost annually. This surveillance-based descriptive epidemiological analysis summarizes data on confirmed human infections between 2018 and 2023, analysing annual incidence rates, 95% confidence intervals, temporal trends, and geographic distribution, while also considering environmental and demographic factors affecting transmission. During the study period, 1677 confirmed infections were reported, including 820 cases (48.9%) of West Nile neuroinvasive disease (WNND) and 116 deaths (6.9%). Annual incidence ranged from 0.095 to 0.996 cases per 100,000 population, with epidemic peaks in 2018 and 2022 and residual endemicity between 2019 and 2021. Regional clustering in the Po Valley suggests ecological suitability linked to riverine plains, agricultural zones, and climatic conditions, while temperature anomalies and rainfall patterns likely influenced mosquito dynamics and viral spread. The integration of standardized incidence rates and confidence intervals highlights the heterogeneous nature of WNV transmission across Italy. Enhanced surveillance during high-risk months (June-September), particularly in Veneto, Emilia-Romagna, and Lombardy, is crucial for timely vector control and blood donor screening. Although symptomatic cases are mandatorily reported, the true infection burden is underestimated due to undetected asymptomatic infections. Serology remains the mainstay of laboratory diagnosis, as no specific antiviral treatment or vaccine is currently available. Prevention relies on mosquito control, elimination of breeding sites, and public awareness measures aimed at reducing exposure and limiting viral transmission. The findings from this analysis can directly inform national arboviral surveillance planning, guide the timing and geographic prioritization of vector control interventions, and support evidence-based blood donor screening policies in Italy and comparable European settings.