High burden of autochthonous arboviral infections during the summer season in Verona province, Italy, during 2025

OBJECTIVES: We aimed at estimating the frequency of local transmission of arboviral infections in Verona province, Italy, between June and September 2025. METHODS: People presenting with acute fever and without recent travel history (and less than WBC 10,000 per µL, unless there was a history of tick bite) were screened for arboviruses following a multi-step protocol. Cases were confirmed by a molecular assay and/or virus-specific IgM antibodies, including rising antibody titre in a second serum sample collected 15-20 days later and a positive seroneutralization test. RESULTS: One hundred and two people were included. Of these, 29 out of 102 (28.4%, 95% CI 20.2-38.4%) demonstrated autochthonous arboviral infections. Specifically, three cases of West Nile fever, four cases of tick-borne encephalitis, and 22 cases of chikungunya infections were diagnosed. CONCLUSIONS: A large proportion of unexplained acute fever cases had arboviral infections from local transmission. Of note, the protocol permitted an early detection of a local outbreak of chikungunya. These findings support the importance of strengthening public health surveillance in southern Europe, for an early detection of transmission foci and to adapt screening protocols to the changing epidemiology of arboviral infections.