About the seasonal surveillance of West Nile virus infections
Most human West Nile virus (WNV) infections occur via mosquito bites; however, people may also become infected through blood transfusion. National public health authorities in the EU/EEA must report human WNV infection case data to the European surveillance portal for infectious diseases (EpiPulse Cases) using the European Union case definition.
ECDC publishes weekly WNV updates on human cases in Europe during the season when cases most commonly occur (usually June to November). ECDC and the European Food Safety Authority (EFSA) also issue monthly WNV reports that integrate surveillance of human cases and animal outbreaks (in equids and birds) and include enhanced analysis and assessment for Europe. Publication of these data informs blood safety, public health and veterinary authorities facilitating the implementation of prevention and control measures.
Prevention of WNV in blood donations
Under the European Union blood safety directives (Directive 2002/98/EC and its implementing directives 2004/33/EC and 2014/110/EU), blood establishments must not accept blood from people who have visited a WNV risk area in the last 28 days, unless an individual nucleic acid test (NAT) performed on them is negative. In line with Europe’s WNV preparedness plan and the ECDC risk assessment tool, an ‘affected area’ or ‘risk area’ is a place with ongoing transmission of WNV to humans. It is defined as having at least one locally acquired human infection. To meet this criterion, at least the first case detected in the area should be confirmed according to the European Union case definition.
Surveillance of WNV in animals
National veterinary authorities must report outbreaks of WNV in animals to the Animal Disease Information System in accordance with Commission Implementing Regulation (EU) 2020/2002. One or more cases of WNV infection detected in animals is considered an outbreak.
While there is no disease-specific case definition for WNV infection in animals, the general case definitions for suspected and confirmed cases laid down in Article 9 of Commission Delegated Regulation (EU) 2020/689 apply, as it is a Category E listed disease under the Animal Health Law.