1. School of social and Community Medicine, University of Bristol, Bristol, UK
2. Bristol Sexual Health Centre, University Hospitals Bristol NHS Foundation Trust, Bristol, UK
3. Chester Sexual Health, Countess of Chester NHS Foundation Trust, Cheshire, UK
4. Public Health Laboratory, Public Health England, Bristol, UK
5. West London Centre for Sexual Health, Chelsea and Westminster Hospital NHS Foundation Trust, London, UK
6. Whittall Street Clinic, Birmingham Sexual Health, University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK