[1] St Marys Hosp, Imperial Coll Sci Technol & Med, Fac Med, Dept Med A, London W2 1NY, England
[2] Univ Witwatersrand, Dept Clin Microbiol & Infect Dis, Reference Ctr Sexually Transmitted Dis, Johannesburg, South Africa
[3] S African Inst Med Res, Johannesburg, South Africa
[4] Statens Serum Inst, DK-2300 Copenhagen, Denmark