1. Department of Paediatrics and Child Health, University of KwaZulu-Natal, Durban, South Africa
2. South African Medical Research Council, HIV Prevention Research Unit, Durban, South Africa
3. South African Medical Research Council, Biostatistics Unit, Durban, South Africa
4. School of Mathematics, Statistics and Computer Science, University of KwaZulu-Natal, Pietermaritzburg, South Africa
5. South African Medical Research Council, Durban, South Africa
6. Occupational Health, Durban, South Africa
7. eThekwini Health Unit, Durban, South Africa