1 University of Zürich Centre for Travel Medicine, WHO Collaborating Centre for Travellers' Health, Zürich, Switzerland. Electronic address: Patricia.Schlagenhauf@uzh.ch.
2 Center of Tropical Medicine and Travel Medicine, Amsterdam University Medical Centers, Location AMC, Amsterdam Infection and Immunity, Amsterdam Public Health, University of Amsterdam, Amsterdam, the Netherlands.
3 School of Public Health and Preventive Medicine, Monash University; and Victorian Infectious Disease Service, Royal Melbourne Hospital, Australia.
4 Pegasus Research, Basel, Switzerland.
5 National Travel Health Network and Centre, University College London Hospital NHS Foundation Trust, London, UK.