[1] Ctr Dis Control & Prevent, Atlanta, GA 30333 USA
[2] Univ Limpopo, Pretoria, South Africa
[3] Assoc Publ Hlth Labs, Washington, DC USA
[4] Natl Inst Communicable Dis, Johannesburg, South Africa
[5] Ahmadu Bello Univ, Zaria, Nigeria
[6] Noguchi Mem Res Inst, Accra, Ghana
[7] Program Appropriate Technol Hlth, Seattle, WA USA
[8] NIH, Bethesda, MD 20892 USA