1. Department of Clinical Microbiology, Uppsala University Hospital, Uppsala
2. Department of Epidemiology, Swedish Institute for Infectious Disease Control, Solna
3. Venhälsan Gay Clinic, Karolinska University Hospital, Stockholm
4. Department of Clinical Microbiology, Karolinska University Hospital Huddinge, Stockholm
5. Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden