Climate change-related factors and west nile virus spread in italy: a systematic review

West Nile Virus (WNV) is a vector-transmitted pathogen affecting both humans and animals, whose presence has recently risen in Europe and particularly in Italy, concurrently with climate changes that favoured the diffusion of mosquitoes. Our review aims to assess such relation with environmental and meteorological factors focusing on the WNV spread in the Italian territory. Following PRISMA guidelines, we performed a literature search in online databases up to May 31, 2023 on four different databases: PubMed, Web of Science, Embase, Scopus. We used keywords and MeSH terms related to WNV and its vectors (C. pipiens and modestus). Following the PECOS criteria, we included observational studies examining vector dynamics and the WNV infection epidemiology in the Italian population and the possible association with environmental factors. The protocol registration on PROSPERO is in process. Out of the 341 articles retrieved, 222 remained after duplicates exclusion and 44 papers were selected after screening of title and abstract by two blinded reviewers. After full-text screening, 31 studies (published between 2011 and 2023) were included. Climatic factors such as temperature, daylight hours and humidity seem to be strongly associated with the spread of WNV and its vectors, while rainfall showed less influence. Among environmental factors, soil characteristics and population dynamics (of both vector and host) were found to be the most predictive. By contrast, distance from specific areas (e.g. urban or protected areas) seems to have no influence. These findings suggest that some climatic and environmental factors linked with climate change strongly affect the presence of WNV and its vectors. This issue can be considered a warning bell about the potential future increase in cases related to climate change, but offers helpful resources for predicting its spread and implement tailored public health interventions.