[1] Columbia Univ, Coll Phys & Surg, Gertrude H Sergievsky Ctr, New York, NY 10032 USA
[2] Univ Witwatersrand, Rahima Moosa Mother & Child Hosp, Empilweni Serv & Res Unit, Johannesburg, South Africa
[3] Univ Witwatersrand, Chris Hani Baragwanath Hosp, Harriet Shezi Clin, Johannesburg, South Africa
[4] Univ Witwatersrand, Dept Mol Med & Haematol, Johannesburg, South Africa
[5] Columbia Univ, Int Ctr AIDS Care & Treatment Programs, New York, NY 10032 USA
[6] Columbia Univ, Dept Biostat, New York, NY 10032 USA
[7] Columbia Univ, Dept Epidemiol, New York, NY 10032 USA
[8] Columbia Univ, Mailman Sch Publ Hlth, New York, NY 10032 USA
[9] Natl Hlth Lab Serv, Johannesburg, South Africa
[10] Natl Inst Communicable Dis, AIDS Res Unit, Johannesburg, South Africa