1. Division of Infectious Diseases and Hospital Epidemiology, University Hospital Zurich, University of Zurich , Zurich , Switzerland
2. Institute of Medical Virology, University of Zurich , Zurich , Switzerland
3. Department of Medicine and Division of Infectious Diseases and Hospital Epidemiology, Kantonsspital Baselland, University of Basel , Bruderholz , Switzerland
4. Division of Infectious Diseases, University Hospital Geneva, University of Geneva , Geneva , Switzerland
5. Division of Infectious Diseases and Hospital Hygiene, University Hospital Basel, University of Basel , Basel , Switzerland
6. Department of Infectious Diseases, Bern University Hospital, University of Bern , Bern , Switzerland
7. Division of Infectious Diseases, University Hospital , Lausanne , Switzerland
8. Division of Infectious Diseases, Regional Hospital Lugano , Lugano , Switzerland
9. Cantonal Hospital St Gallen, Division of Infectious Diseases and Hospital Epidemiology , St Gallen , Switzerland