1. School of Social and Community Medicine, University of Bristol, UK
2. Bristol Sexual Health Centre, University Hospitals Bristol NHS Foundation Trust, UK
3. Department of Dermatology and Venereology, Linköping University Hospital, Sweden
4. Department of Clinical and Experimental Medicine, Linköping University, Sweden
5. Department of Dermatology, New Cross Hospital, UK
6. Olafia Clinic, Oslo University Hospital, Institute of Medicine, University of Oslo, Norway