[1] Univ KwaZulu Natal, Ctr Rural Hlth, ZA-4013 Durban, South Africa
[2] Univ KwaZulu Natal, Dept Publ Hlth, ZA-4013 Durban, South Africa
[3] Univ KwaZulu Natal, Dept Paediat & Child Hlth, ZA-4013 Durban, South Africa
[4] WHO, Dept Child & Adolescent Hlth & Dev, CH-1211 Geneva 27, Switzerland