[1] Univ Witwatersrand, Dept Virol, Natl Inst Virol, MRC,AIDS Virus Res Unit, Johannesburg, South Africa
[2] Univ Witwatersrand, Dept Community Hlth, ZA-2001 Johannesburg, South Africa
[3] Baragwanath Hosp, Dept Neurol, ZA-2013 Johannesburg, South Africa
[4] S African Inst Med Res, Dept Chem Pathol, Johannesburg, South Africa
[5] S African Inst Med Res, Dept Med Microbiol, Johannesburg, South Africa