The 1993 Okey Memorial Lecture. Cross-national studies of AIDS among injecting drug users.

HIV infection among injecting drug users has become a world-wide public health problem. This raises fundamental questions about the modifiability of drug-using behavior and of the influence of different national settings upon the modification of drug use behavior. Data from the World Health Organization Multi-site Study of HIV and Injecting Drug Use and studies of HIV among drug injectors in New York City (the US component of the WHO study) are used to address these questions. There is no clear relationship between HIV seroprevalence and current levels of risk behavior in the WHO cities, and the range in seroprevalence is much greater than the range in current risk behavior. Nonetheless, historical trend data enable us to discern at least two broad patterns in different cities. HIV epidemics appear to have been successfully prevented among IDUs in some cities, in that seroprevalence has remained low and stable over several years. These cities are characterized by community outreach programs and good access to sterile injection equipment. On the other hand, high seroprevalence epidemics have also occurred in many different cities. Stabilization of seroprevalence has eventually also occurred in these cities, but this still includes moderate rates of new HIV infections. How to reverse high-seroprevalence situations remains one of the more difficult questions in HIV epidemiology. The epidemiology of HIV infection among injecting drug users also needs to include analyses of the impacts of decisions by political and public health leaders. A three-category scheme for classifying political decisions is offered: data-free decisions, data-based decisions, and data-proof decisions.