Columbia University - Irving Medical Center, Columbia University - Irving Medical Center, University of the Witwatersrand, Yale University, University of the Witwatersrand, University of the Witwatersrand, University of KwaZulu-Natal, Stellenbosch University, University of KwaZulu-Natal, affiliation not provided to SSRN, University of the Witwatersrand, University of the Witwatersrand, University of KwaZulu-Natal, Columbia University, Columbia University - Department of Medicine, World Health Organization (WHO) - International Agency for Research on Cancer (IARC), University of the Witwatersrand, University of the Witwatersrand and Columbia University - Irving Medical Center