1 Department of Public Health/Division of Infectious Diseases, Epidemiology, Biostatistics and Prevention Institute, University of Zurich, Zurich, Switzerland.
2 Department of Tropical Medicine, Bernhard Nocht Institute for Tropical Medicine and I. Department of Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
3 Centre de Recherches Médicales de Lambaréné, Albert Schweitzer Hospital, Lambaréné, Gabon.