In addition, participants in both groups will attend drug and risk reduction counseling weekly. After the first 12 weeks, participants will return every 4 weeks for 10 more counseling sessions. HIV testing, hepatitis C testing, risk assessment, and urine tests for opiates will occur at screening and at Weeks 26, 52, 78, 104, 130 and 156. Plasma from blood samples will be stored at each of these visits. Hepatitis B testing will occur at Week 26. Participants in China will attend study visits through approximately Week 104, and participants in Thailand will attend study visits through approximately Week 156.