HIV among injecting drug users in Bangkok: The first decade

Abstract

Objective: To examine the long-term structure of the high human immunodeficiency virus (HIV) prevalence epidemic among injecting drug users (IDUs) in Bangkok, Thailand. Methods: Annual HIV seroprevalence surveys were conducted at the drug abuse treatment clinics of the Bangkok Metropolitan Administration (BMA) from 1987 onward. Risk behavior surveys were conducted in 1989, 1993 and 1997. A large cohort study to measure HIV incidence was also conducted in the BMA drug treatment clinics from 1995 to 1998. Results: HIV prevalence rose rapidly in 1988 and then remained stable at 30-40%. A very high percentage (over 90%) of IDUs reported reducing risk behavior by the fall of 1989, with injection risk behavior declining from 1989 through 1997. Sexual risk behavior occurred mostly within primary relationships. Estimated HIV incidence was moderate to high at 5.8/100 person-years at risk from 1995 to 1998. Incarceration and injecting while incarcerated were strongly associated with incident HIV infections. Conclusions: The initial risk reduction served to reduce HIV transmission and stabilize the epidemic, preventing saturation of HIV within IDUs in Bangkok. Significant levels of risk behavior persisted, however, leading to a 'moderate to high' incidence rate. Successfully addressing a high seroprevalence HIV epidemic among IDUs will probably require multiple, large-scale prevention efforts maintained over long time periods.