1. Department of Infectious Diseases, Municipal Public Health Service, Rotterdam (The National Institute for STD and AIDS Control in the Netherlands), The Netherlands
2. STI AIDS Netherlands, The Netherlands
3. Municipal Health Service Eastern South Limburg, Heerlen, The Netherlands
4. Municipal Health Service Groningen, The Netherlands
5. Municipal Health Service 'Hart voor Brabant', Tilburg, The Netherlands
6. Department of Infectious Diseases, Municipal Public Health Service, Rotterdam (The National Institute for STD and AIDS Control in the Netherlands), The Netherlands; Department of Public Health, Erasmus MC,
University Medical Center Rotterdam, Rotterdam, The Netherlands