1 Infection Control Programme, University of Geneva Hospitals and Faculty of Medicine, Geneva, Switzerland.
2 Imperial College London, London, UK.
3 European Centre for Disease Prevention and Control, Stockholm, Sweden.
4 Infection Control Programme, University of Geneva Hospitals and Faculty of Medicine, Geneva, Switzerland; WHO Collaborating Centre on Patient Safety, University of Geneva Hospitals and Faculty of Medicine, 1211 Geneva 14, Switzerland. Electronic address: didier.pittet@hcuge.ch.