1. Department of Infectious Diseases, Karolinska University Hospital, Stockholm, Sweden
2. Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden
3. Clinical Research Department, Bernhard-Nocht-Institute for Tropical Medicine, Hamburg, Germany
4. Division of Infectious Diseases, I. Department of Internal Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
5. Department of Infectious Diseases, Västmanland Hospital, Västerås, Sweden
6. Public Health Agency of Sweden, Stockholm, Sweden
7. Robert Koch Institute, Berlin, Germany
8. Department of Pediatrics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
9. Unit of Biostatistics, Department of Epidemiology, Institute for Environmental Medicine, Karolinska Institutet, Stockholm, Sweden
10. Department for Early Warning and Surveillance Center for Epidemiology and Surveillance of Infectious Diseases, National Institute for Public Health and the Environment, Bilthoven, the Netherlands
11. Public Health England, London, United Kingdom
12. Federal Office of Public Health, Bern, Switzerland
13. Statens Serum Institute, Copenhagen, Denmark