aDesmond Tutu HIV Centre, Institute for Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South AfricabClinical Research Unit, Department of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, UKcHIV Unit, Ministry of Health, MalawidFamily Health International, Malawi Country Office, Lilongwe, MalawieProgramme PAC-CI, Abidjan, Ivory Coast, FrancefINSERM, Unité 897, Centre de Recherche Epidémiologie et Biostatistique, Bordeaux, FrancegInfectious Diseases Epidemiology Unit, School of Public Health and Family Medicine, Faculty of Health Sciences, University of Cape Town, Cape Town, South AfricahDepartment of Epidemiology, Mailman School of Public Health, Columbia University, New York, USA.