1. Institute of Public Health, Medical School, Heidelberg University, Im Neuenheimer Feld 324, 69120 Heidelberg, Germany.
2. Centre de Recherche en Santé de Nouna (CRSN), BP02 Nouna, Burkina Faso.
3. Institute of Medical Biometry and Epidemiology, University Medical Center Hamburg–Eppendorf, Hamburg, Germany.