1 National Institutes of Health, Bethesda, MD, USA. Electronic address: Cgodfrey@niaid.nih.gov.
2 Harvard T H Chan School of Public Health, Boston, MA, USA.
3 HIV Management, Enhancing Care Foundation, Durban, South Africa.
4 Department of Molecular Medicine and Haematology, School of Pathology, Faculty of Health Science, University of the Witwatersrand, Johannesburg, South Africa.
5 HIV Management, Epidemiology, Sizwe Tropical Diseases Hospital, Johannesburg, South Africa.