1. These authors contributed equally
2. Infection Control Programme and WHO Collaborating Centre on Patient Safety, University of Geneva Hospitals and Faculty of Medicine, Geneva, Switzerland
3. Infection Control Programme, Cantonal Hospital Authority, Ticino, Switzerland
4. Institute of Hygiene and Environmental Medicine, Charité University Medicine Berlin, Berlin, Germany
5. Swiss Federal Office of Public Health, Bern, Switzerland
6. Division of Infectious Diseases and Hospital Epidemiology, University Hospital Basel, Switzerland