High HIV seroprevalence epidemics among injecting drug users; New York City and Bangkok

New York City, U.S.A., and Bangkok, Thailand, experienced two of the most important HIV epidemics among injecting drug users (IDUs) in the world. The epidemic in New York was the first, and by far the largest, HIV epidemic among IDUs. The Bangkok epidemic was notable both for the rapidity of HIV transmission among IDUs and for demonstrating that HIV transmission could occur among IDUs in developing countries. Rapid HIV transmission among IDUs in both cities was followed by large-scale behavior change and stabilization of HIV seroprevalence at high levels. The stabilization of seroprevalence includes unacceptably high rates of continued HIV seroconversions-estimated to be 4 per 100 person-years at risk or greater in both cities. Recent additional HIV prevention efforts in both cities-long-term methadone maintenance treatment in Bangkok and legal access to sterile injection equipment in New York-indicate possibilities for further reducing HIV transmission among IDUs in the two cities.