The influenza virus changes constantly. Virological and disease surveillance is crucial to determine the impact of the disease and identify the circulating strains.

Member States collect data on: 

• the epidemiology and virology of seasonal epidemics; 
• outbreaks of avian influenza in animals and humans; and 
• outbreaks of other influenza viruses with pandemic potential.

WHO/Europe and the ECDC are performing joint surveillance of seasonal influenza in the region and as of 13 February 2009, a weekly regional bulletin for seasonal influenza is published on the EISS website in English and Russian. The bulletin contains epidemiological and virological data from those countries in the European Region that perform influenza surveillance and which report to the EISS platform. The data is collected by clinicians networks and laboratory networks, consisting mainly of WHO-recognized National Influenza Centres (NIC).

The regional surveillance network also participates in the WHO Global Influenza Surveillance Network (GISN), mainly through the NIC of which there are 50 in 39 European countries. Data and viruses are submitted through the NIC and the surveillance focal points to one of the four global WHO Collaborating Centres for Reference and Research on influenza (WHO CC) in the UK. This enables WHO to recommend the composition of the influenza vaccine for the following season and is done twice a year, for the northern and for southern hemispheres. In addition, WHO CC determine patterns of antiviral susceptibility of circulating strains and update reagents. The GISN also acts as a global alert mechanism for the appearance of influenza viruses with pandemic potential.

In the WHO European Region, there is also a WHO H5 reference laboratory in France.