1. Ifakara Health Institute , Ifakara , Tanzania
2. Division of Epidemiology and Biostatistics, University of the Witwatersrand , Johannesburg , South Africa
3. Division of Infectious Diseases and Hospital Epidemiology, University Hospital of Basel , Basel , Switzerland
4. Swiss Tropical and Public Health Institute , Basel , Switzerland
5. Department of Family Medicine and Primary Care, University of the Witwatersrand , Johannesburg , South Africa