Repeated detection of West Nile virus in Aedes caspius during an unusually early transmission season in humans in northern Italy, 2026
Mario Chiari, Francesco Defilippo, Davide Lelli, Luigi Vezzosi, Danilo Cereda, Gabriele Del Castillo, Francesco Maraschi, Angela Ancona, Giuliano Rizzardini, Anna Marelli, Ambra Nucci, Moira Bazzucchi, Maria Gabriella Perrotta, Marino Faccini, Marinella Valenti, Simone Villa, Davide Mileto, Alessandra Lombardi, Alessandro Mancon, Valeria Micheli, Andrea Gori, Stefania Piconi, Greta Romano, Guglielmo Ferrari, Antonio Piralla, Francesca Rovida, Ana Moreno, Fausto BaldantiIn Lombardy, northern Italy, 2026, the first neuroinvasive West Nile virus (WNV) human case was reported on 7 July. Concurrently, high abundances of Aedes caspius and low numbers of Culex pipiens occurred at several surveillance sites. Testing seven archived Ae. caspius pools collected in July revealed WNV lineage 2 in six pools from three independent sites. A virus sequence from Ae. caspius shared > 99.94% nt identity with contemporaneous human-derived sequences. Further investigating possible Ae. caspius vector competence, particularly for WNV lineage 2, is warranted.