1. Robert Koch Institute, Berlin, Germany
2. European Centre for Disease Prevention and Control (ECDC), Stockholm, Sweden
3. Health Protection Surveillance Centre, Dublin, Ireland
4. Institut de Veille Sanitare, Saint-Maurice, France
5. National Institute of Public Health – National Institute of Hygiene, Warsaw, Poland
6. Statens Serum Institut, Copenhagen, Denmark
7. Istituto Superiore di Sanitá, Rome, Italy
8. Members of the VENICE III NITAG Survey Group are listed at the end of the article