Epidemiological update: West Nile virus transmission season in Europe, 2021

Human infections

As of 10 February 2022, European Union (EU), European Economic Area (EEA) and EU-neighbouring countries reported 164 human cases of West Nile virus (WNV) infection in 2021, of which 159 were locally acquired and five were travel related.

During the 2021 transmission season, EU/EEA countries reported 139 locally acquired human cases of WNV infection with known place of infection, including 10 deaths, through The European Surveillance System (TESSy). Cases were reported by Greece (57), Italy (55), Hungary (7), Romania (7), Spain (6), Germany (4) and Austria (3). Greece reported two additional locally acquired human cases with unknown place of infection at NUTS3 level. Deaths were reported by Greece (8), Romania (1) and Spain (1).

Human WNV infections were reported in seven EU Member States and one EU-neighbouring country where seasonal circulation of the virus had been previously reported. Burgenlandkreis and Spree-Neisse in Germany and La Spezia in Italy reported locally acquired human cases of WNV infection for the first time. All other cases reported through TESSy were from areas that had been affected during previous transmission seasons.

Five travel-related cases of WNV infection were reported this transmission season, associated with travel to the United States (3), Mayotte (1) and Cyprus (1). No deaths were reported among these cases.

EU-neighbouring countries reported 18 human cases of WNV infection, including three deaths; all were reported by Serbia.

The first locally acquired case of the season in the EU was notified by Italy in week 26 (26 June to 4 July), with disease onset in week 24 (14 to 20 June). The last case was reported by Greece in week 45 (8 to 14 November), with disease onset in week 43 (25 to 31 October).

Animal outbreaks

Animal data are collected through the  Animal Disease Information System (ADIS) of the European Commission. The distribution reports for WNV outbreaks among equids and birds cover only EU/EEA countries.

During the 2021 transmission season, seven EU/EEA countries reported 43 outbreaks among equids: Germany (16), Spain (11), Italy (6), Portugal (4), Hungary (3), France (2) and Greece (1). In addition, eight outbreaks among birds were reported by Spain (7) and Slovenia (1).