1. Glasgow Caledonian University, Glasgow, United Kingdom
2. Health Protection Scotland, Glasgow, United Kingdom
3. Public Health England, London, United Kingdom
4. University College London, United Kingdom (current affiliation)
5. National Institute for Health and Welfare, Helsinki, Finland
6. Institut de Veille Sanitaire, Saint-Maurice, France
7. Charité University Medicine Berlin, Germany
8. European Centre for Disease Prevention and Control (ECDC), Stockholm, Sweden
9. The participants are listed at the end of the article