1. Patrick Manson Unit, University College London Hospitals, London, UK
2. Patrick Manson Unit, University College London Hospitals, London, UK; Department of Genitourinary Medicine, Mortimer Market Centre, Camden PCT, London, UK
3. Patrick Manson Unit, University College London Hospitals, London, UK; Centre for Sexual Health and HIV Research, Department of Population Sciences and Primary Care, Royal Free and University College Medical School, University
College London, London, UK