Weekly updates: 2021 West Nile virus transmission season


This weekly report provides an overview of West Nile virus (WNV) epidemiology in the EU/EEA and EU-neighbouring countries during the WNV transmission season (expected to be June-November). Following a One Health approach, WNV infections in humans and outbreaks in equids and birds are included in the report. Visit the dedicated webpages for more information on WNV infections and ECDC’s seasonal WNV surveillance.

Situation update

The last weekly epidemiological update of the 2021 WNV transmission season was published on 12 November 2021.

Between 5 and 11 November 2021, European Union (EU) and European Economic Area (EEA) countries reported one human case of West Nile virus (WNV) infection and no deaths related to WNV infections. The case was reported by Greece. EU-neighbouring countries reported no human cases of WNV infection and no deaths related to WNV infections.

Since the beginning of the 2021 transmission season and as of 11 November 2021, EU/EEA countries have reported 139 human cases of WNV infection in Greece (57), Italy (55), Hungary (7), Romania (7), Spain (6), Germany (4) and Austria (3) and 9 deaths in Greece (7), Spain (1) and Romania (1). EU-neighbouring countries have reported 18 human cases of WNV infection in Serbia (18) and 3 deaths in Serbia (3).

During the current transmission season, within the reporting countries, human cases of WNV infection were reported from 46 different NUTS 3 or GAUL 1 regions, of which the following regions reported human cases of WNV infection for the first time: Burgenlandkreis and Spree-Neiße in Germany and La Spezia in Italy.

Since the beginning of the 2021 transmission season, 37 outbreaks among equids and 8 outbreaks among birds have been reported by EU/EEA countries. Outbreaks among equids have been reported by Germany (16), Spain (11), Portugal (4), Hungary (3), France (2) and Greece (1). Outbreaks among birds have been reported by Spain (7) and Slovenia (1).


Data on human cases are collected via The European Surveillance System (TESSy) managed by ECDC. Only locally acquired cases with known place of infection are included in this report. The following EU-neighbouring countries report human cases of WNV infection to ECDC: Albania, Kosovo*, Montenegro, North Macedonia, Serbia and Turkey.

Animal data (i.e. outbreaks among equids and birds) are collected through the Animal Disease Information System (ADIS) of the European Commission. Reporting of WNV in equids and birds is mandatory at the EU/EEA level.

The distribution of human infections covers EU/EEA and EU-neighbouring countries, whereas outbreaks among equids and birds covers only EU/EEA countries.

* This designation is without prejudice to positions on status, and is in line with UNSCR 1244/1999 and the ICJ Opinion on the Kosovo declaration of independence

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Case definition

EU case definition for diagnosing and reporting West Nile virus infection, under Decision No 2119/98/EC of the European Parliament and of the Council.

See West Nile virus infection

ECDC publishes weekly WNV epidemiological updates during the WNV transmission season, including the geographical distribution of human cases in the EU/EEA and EU neighbouring countries. In addition, ECDC includes maps in its epidemiological updates highlighting areas where WNV outbreaks among equids have been reported. Read more