1. School of Public Health, Shanxi Medical University, Taiyuan, Shanxi, China
2. Center of Clinical Epidemiology and Evidence Based Medicine, Shanxi Medical University, Taiyuan, Shanxi, China
3. Shanxi Provincial Center for Disease Control and Prevention, Taiyuan, Shanxi, China
4. Methadone Maintenance Treatment Clinic, Compulsory Isolation Drug Rehabilitation Center, Taiyuan, Shanxi, China
5. Xinghualing District Methadone Maintenance Treatment Clinic, Taiyuan, Shanxi, China
6. Methadone Maintenance Treatment Clinic, 109 Hospital, Taiyuan, Shanxi, China
7. Chinese Center for Disease Control and Prevention, Beijing, PR China
8. Chinese Preventive Medicine Association, Beijing, China