1 University of Zürich, 8001, Zürich, Switzerland.
2 University of Zürich, Epidemiology, Biostatistics and Prevention Institute, Department of Public Health, Hirschengraben 84, 8001, Zürich, Switzerland.
3 WHO Collaborating Centre for Travellers' Health, Department of Global and Public Health, MilMedBiol Competence Centre, Hirschengraben 84, 8001, Zürich, Switzerland.