[1] Univ London Imperial Coll Sci Technol & Med, Dept Infect Dis & Microbiol, London, England
[2] Univ London Imperial Coll Sci Technol & Med, Dept Infect Dis Epidemiol, London, England
[3] Hlth Protect Agcy, Sexually Transmitted Bacteria Reference Lab, SRMD,HIV STI Div, Ctr Communicable Dis Surveillance, London NW9 5HT, England
[4] Royal Free & UCL, Dept Primary Care, Sch Med, London, England
[5] Royal Free & UCL, Dept Populat Sci, Sch Med, London, England
[6] Royal Free & UCL, Dept Sexually Transmitted Dis, Sch Med, London, England