[1] Univ Cape Town, Dept Paediat & Child Hlth, Red Cross War Mem Childrens Hosp, ZA-7700 Rondebosch, South Africa
[2] Univ Cape Town, Med Res Council, Unit Child & Adolescent Hlth, Fac Hlth, ZA-7700 Rondebosch, South Africa
[3] Univ Cape Town, Med Res Council, Unit Child & Adolescent Hlth, Fac Hlth Sci, ZA-7700 Rondebosch, South Africa
[4] Univ Cape Town, Fac Hlth Sci, Sch Publ Hlth & Family Med, Div Epidemiol & Biostat, ZA-7700 Rondebosch, South Africa
[5] Univ Cape Town, Fac Hlth Sci, Div Med Microbiol, Dept Pathol, Cape Town, South Africa
[6] Natl Hlth Lab Serv, Cape Town, South Africa