1. Department of Dermatology; Venerology and Allergology; Center for Sexual Health and Medicine; Ruhr-Universität Bochum; Bochum Germany
2. Competence Network for HIV/AIDS; Ruhr-Universität Bochum; Bochum Germany
3. Department of Addiction Medicine and Addictive Behaviour; LVR-Klinikum Essen; Hospital of the University of Duisburg-Essen; Essen Germany
4. Department of Dermatology and Venerology; University Hospital Duisburg-Essen; Essen Germany