1. Epidemiology, Biostatistics and Prevention Institute, Department of Public Health, Division of Infectious Diseases/Travel Clinic, University of Zurich, Hirschengraben 84, 8001 Zurich, Switzerland
2. Division of Tropical and Humanitarian Medicine, Geneva University Hospitals, Rue Gabrielle-Perret-Gentil 6, 1205 Geneva, Switzerland
3. Department of Medicine and Diagnostics, Swiss Tropical and Public Health Institute, Socinstrasse 57, 4051 Basel, Switzerland