[1] Univ Witwatersrand, Fac Hlth Sci, Sch Clin Med, Hlth Econ & Epidemiol Res Off,Dept Internal Med, Johannesburg, South Africa
[2] Univ N Carolina Chapel Hill, Gillings Sch Global Publ Hlth, Dept Epidemiol, Chapel Hill, NC 27599 USA
[3] Witkoppen Hlth & Welf Ctr, Johannesburg, South Africa
[4] Univ N Carolina Chapel Hill, Sch Med, Div Infect Dis, Chapel Hill, NC 27599 USA
[5] Boston Univ, Ctr Global Hlth & Dev, Boston, MA 02215 USA
[6] Boston Univ, Sch Publ Hlth, Dept Epidemiol, Boston, MA USA