Deaths have occurred in Piemonte, Lombardia, and Emilia Romagna, prompting concern among health officials.
The first human case of West Nile infection this season was reported in July in the province of Parma in Emilia Romagna.
Additionally, five cases of the Usutu virus were identified, four among blood donors and one case manifested in a neuro-invasive form. The West Nile virus is currently circulating in 52 provinces across 10 regions.
Updated epidemiological data as of 27th September 2023 reveals that European Union (EU) and European Economic Area (EEA) countries reported 85 human cases of West Nile virus (WNV) infection and six related deaths in the past week. Italy accounted for the majority of these cases, reporting 50 new infections and four deaths.
Notably, the virus has spread to new regions for the first time this season. These include Ioannina in Greece, Cáceres in Spain, Charente, Gard and Vaucluse in France, and Taranto and Lecce in Italy. Since the beginning of the 2023 transmission season, EU/EEA countries have reported 566 human cases of WNV infection, with Italy bearing the brunt of these infections at 280 cases.
Italy’s adoption of the “One Health Approach” for monitoring the virus includes four laboratory criteria for case confirmation, such as the isolation of the virus from the cerebrospinal fluid or blood of the host, detection of viral nucleic acid, the presence of viral antigen-specific immunoglobulin M response in the cerebrospinal fluid, and the presence of high titers of viral IgM antibody and detection of viral IgG antibody using neutralization for confirmation.
A recent article published in Eurosurveillance described the seasonal transmission of the West Nile virus in 2022 and made a comparison with the reports in 2018. The first West Nile virus infection in Italy in 2022 occurred in birds and mosquitoes in early June. Human infection by the virus started being detected on June 19th. By July, human cases surged with two strains of the virus co-circulating simultaneously.
This summer, Italy has seen a dramatic increase in cases of West Nile fever. In the last week alone, 50 more cases have been reported, bringing the total number of cases in the northern regions of Veneto, Piemonte, Lombardia, and Emilia Romagna to 144. This alarming trend has led to three more patients dying in the last seven days, bringing the virus’s total death toll up to 10.
The city of Padova in Veneto is considered the hotspot of the virus in the country. Despite southern Italy being hotter and more humid, providing a better habitat for the virus-carrying mosquitoes, the lowlands of Veneto with their natural habitat are actually the perfect breeding ground for mosquitoes.
Italy has implemented many vector control measures following the 2018 epidemic. These planned measures were executed in 2022. Although no transfusion-associated case was found, blood safety measures were implemented in many provinces owing to the rise in human cases.
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