1. Department of Infectious Diseases, Institut de Veille Sanitaire (InVS, French Institute for Public Health Surveillance), Paris, France
2. National Centre for Epidemiology, Surveillance and Health Promotion, Istituto Superiore di Sanità (ISS, National Institute of Health), Rome, Italy
3. CINECA Consortium of Universities, Bologna, Italy
4. Health Protection Surveillance Centre (HPSC), Dublin, Ireland
5. National Institute of Public Heath- National Institute of Hygiene, Warsaw, Poland
6. Scientific Advice Unit, European Centre for Disease Prevention and Control (ECDC), Stockholm, Sweden
7. The members of the group are listed at the end of the article