1. Laboratory for Infectious Diseases and Screening, Rijksinstituut voor Volksgezondheid en Milieu (National Institute of Public Health and the Environment, RIVM), Bilthoven, the Netherlands
2. European Influenza Surveillance Scheme (EISS) Co-ordination Centre, Nederlands Instituut voor Onderzoek van de Gezondheidszorg (Netherlands Institute for Health Services Research, NIVEL), Utrecht, the Netherlands
3. European Surveillance Network for Vigilance against Viral Resistance (VIRGIL)
4. Respiratory Virus Unit, Centre for Infection, Health Protection Agency, London, United Kingdom
5. World Health Organization Collaborating Centre for Reference and Research on Influenza, National Institute for Medical Research, London, United Kingdom