Epidemiological update: West Nile virus transmission season in Europe, 2022

Human infections 

As of 30 June 2023, European Union (EU) and European Economic Area (EEA) countries have reported 1 133 human cases of West Nile virus (WNV) infection through The European Surveillance System (TESSy), including 92 deaths for 2022, of which 1 113 were locally acquired, 17 were travel-related, and three had an unknown importation status and unknown place of infection.   

Ten EU/EEA countries reported 1 108 locally acquired human cases of WNV infection with known place of infection at NUTS3 level. These locally acquired cases were reported by Italy (723), Greece (283), Romania (47), Germany (16), Hungary (14), Croatia (8), Austria (6), France (6), Spain (4), and Slovakia (1). Deaths were reported by Italy (51), Greece (33), Romania (5), and Hungary (3).  Greece reported three and Bulgaria and Germany each reported one additional locally acquired human case with unknown place of infection at NUTS3 level. Italy reported two cases and Finland reported one additional case with unknown importation status and unknown place of infection.  

EU-neighbouring countries reported 228 human cases of WNV infection, including 12 deaths, of which 227 were locally acquired and one was related to travel to Türkiye. Cases were reported by Serbia (226) and North Macedonia (two, one of which was travel-related).  

In 2022, within the reporting countries human cases of WNV infection were reported from 115 different NUTS 3 or GAUL 1 regions, of which the following regions reported human cases of WNV infection for the first time: Bouches-du-Rhône in France, Harz, Vogtlandkreis, Salzlandkreis, Dahme-Spreewald, Magdeburg Kreisfreie Stadt and Teltow-Fläming in Germany, Pistoia, Lucca, Monza e della Brianza, Biella, Cagliari, Catania and Lecco in Italy, Grad Zagreb and Zagrebačka županija in Croatia, Severoistočen in North Macedonia, Moravicki in Serbia, and Tarragona and Córdoba in Spain. All other cases reported through TESSy were from areas that have been affected during previous transmission seasons.  

EU/EEA countries reported 17 travel-related cases of WNV infection this transmission season, associated with travel to Italy (6), Greece (2), Serbia (2), Morocco (2), Croatia (1), Senegal (1), Spain (1), Israel (1), and the United States (1). No deaths were reported among these cases. 

An exceptionally early locally acquired case, with disease onset on 16 April, was reported by Italy, while the second locally acquired case had 19 June as date of onset (also reported by Italy). The last cases were reported by Greece and Italy, with disease onset on 4 and 5 November, respectively. An additional case was reported by France with reported disease onset on 12 December), but it should be noted that the case was immunosuppressed and this may have interfered with and prolonged the duration of the incubation period. It may also have contributed to the long period of viremia. 

Two EU countries (Italy and Greece) and one EU-neighbouring country (Serbia) reported high numbers of human WNV cases of infection in 2022. The number of cases in Italy in 2022 was the highest on record. 

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 only cover EU/EEA countries. 

In 2022, nine EU/EEA countries reported 101 outbreaks among equids and 323 outbreaks among birds. Outbreaks among equids were reported by Italy (47), Germany (16), Greece (9), Spain (8), Croatia (8), France (6), Hungary (3), Portugal (3), and Austria (1). These were more than twice as many outbreaks reported as for 2021, but only around half and one third of reported outbreaks for 2020 and 2018, respectively. In Italy, this was the highest number of outbreaks reported since 2018. Outbreaks among birds were reported by Italy (258), Germany (51), Spain (9), Austria (2), Croatia (2), and Hungary (1). With the exception of Portugal, all these countries also reported human WNV infections in 2022.