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Abstract In the last fifteen years, the West Nile virus (WNV) has spread in the Po Valley plain in Italy, extending from Emilia-Romagna to Veneto in Friuli Venezia Giulia, Lombardy, and Piedmont regions. The principal vector of WNV in Italy is Culex pipiens, and lineage 2 of arbovirus can overwinter. The sensitivity of the mosquito surveillance network to the circulation of WNV in urban and rural areas and the impact of the ecological system on the dynamics and spillover of disease were investigated in this study. WNV circulation in mosquitoes collected in 2021–2023 and screened with RT-PCR differed between the two environments. The vector index (VI) was significantly higher for Culex pipiens collected in rural areas and near rural wetlands (VI = 0.08 ± 0.16 SD and VI = 0.15 ± 0.29 SD respectively) than in urban environments (from VI = 0.00 in urban parks to VI = 0.04 ± 0.13SD in peri-urban areas). The incidence of West Nile neuroinvasive disease was higher in rural (1.01 ± 0.59SD per 100.000 inhabitants) than in urban areas (0.43 ± 0.32SD cases per 100.000 inhabitants). Throughout the study duration, by monitoring the virus circulation in mosquitoes, the WNV surveillance in the urban ecosystem predicted spillover in humans with about 2–4 weeks of anticipation, allowing prompt activation of the control protocols defined in the Italian National Plan Surveillance and Control for Arboviruses. WNV circulation in mosquitoes was recorded in urban environments where the probability of the simultaneous presence of reservoirs and vectors was higher such as ecological corridors and peri-urban areas. No WNV circulation was found in mosquitoes in urban parks.
Carrieri et al. (Sat,) studied this question.