1. Division of Infectious Diseases and Hospital Epidemiology, University Hospital Zurich, Switzerland
2. Institute of Medical Virology, University of Zurich, Switzerland
3. Department of Infectious Diseases and Hospital Hygiene, University Hospital Basel, University of Basel, Switzerland
4. Department of Infectious Diseases, Bern University Hospital, University of Bern, Switzerland
5. Division of Infectious Diseases, University Hospital Lausanne, University of Lausanne, Switzerland
6. Division of Infectious Diseases and Hospital Epidemiology, Kantonal Hospital St Gallen, Switzerland