[1] Univ Rochester, Dept Emergency Med, Rochester, NY 14642 USA
[2] Univ Rochester, Dept Community & Prevent Med, Rochester, NY 14642 USA
[3] McGill Univ, Dept Epidemiol Biostat & Occupat Hlth, Montreal, PQ, Canada
[4] Univ Witwatersrand, Perinatal HIV Res Unit, Johannesburg, South Africa
[5] Johns Hopkins Univ, Sch Med, Baltimore, MD USA
[6] Univ Witwatersrand, Dept Anat Pathol, Div Cytol, Johannesburg, South Africa
[7] Natl Lab, Hlth Serv, Johannesburg, South Africa