1. Public Health Directorate Castilla y León Regional Health Ministry Valladolid Spain
2. The Radboud University Nijmegen Medical Centre Nijmegen The Netherlands
3. European Centre for Disease Prevention and Control Stockholm Sweden
4. Division of Health Security, Infectious Diseases and the Environment WHO Regional Office for Europe Copenhagen Denmark
5. National Influenza Centre University of Valladolid Valladolid Spain
6. Health Protection Surveillance Centre Dublin Ireland
7. Laboratoire National de Santé Luxembourg Luxembourg
8. Statens Serum Institute Copenhagen Denmark
9. Division of Communicable Diseases Federal Office of Public Health Directorates of Public Health Bern Switzerland
10. CIBER Epidemiología y Salud Pública (CIBERESP) Institute of Health Carlos III Madrid Spain