[1] Univ Cape Town, Sch Publ Hlth & Family Med, Div Social & Behav Sci, Cape Town, South Africa
[2] Univ Cape Town, Sch Publ Hlth & Family Med, Ctr Infect Dis Epidemiol & Res, Cape Town, South Africa
[3] Univ Cape Town, Sch Publ Hlth & Family Med, Div Epidemiol & Biostat, Cape Town, South Africa
[4] Columbia Univ, Mailman Sch Publ Hlth, ICAP, New York, NY USA
[5] Columbia Univ, Coll Phys & Surg, New York, NY USA