1. Gay Men's Sexual Health Research Group, School of Population Health, University of Auckland Auckland New Zealand
2. AIDS Epidemiology Group, Department of Preventive and Social MedicineUniversity of Otago Dunedin New Zealand
3. Needle Exchange Services Trust, New Zealand Needle Exchange Programme Christchurch New Zealand
4. Centre for Addiction Research, Faculty of Medical and Health Sciences, University of Auckland Auckland New Zealand
5. Greymouth New Zealand