1 WHO Collaborating Centre for Travellers' Health, Department of Global and Public Health, Epidemiology, Biostatistics and Prevention Institute, University of Zurich, Hirschengraben 84, 8001, Zurich, Switzerland; MilMedBiol -Center of Competence for Military Medicine Biology, University of Zurich, Zurich, Switzerland. Electronic address: patricia.schlagenhauf@uzh.ch.
2 WHO Collaborating Centre for Travellers' Health, Department of Global and Public Health, Epidemiology, Biostatistics and Prevention Institute, University of Zurich, Hirschengraben 84, 8001, Zurich, Switzerland.
3 Center of Tropical Medicine and Travel Medicine, Department of Infectious Diseases, Amsterdam University Medical Centers, location AMC, Amsterdam Infection & Immunity, Amsterdam Public Health, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, Amsterdam, the Netherlands.