1 Division of Infectious Diseases and Hospital Epidemiology, University Hospital Basel, University of Basel, Switzerland / Basel Institute for Clinical Epidemiology and Biostatistics, University Hospital Basel, University of Basel, Switzerland.
2 Epidemiology, Biostatistics and Prevention Institute, University of Zurich, Switzerland.
3 Division of Infectious Diseases and Hospital Epidemiology, University Hospital Zurich, University of Zurich, Switzerland / Institute of Medical Virology, University of Zurich, Switzerland.
4 Division of Infectious Diseases and Hospital Epidemiology, University Hospital Basel, University of Basel, Switzerland.