HIV infection and intravenous drug use: critical issues in transmission dynamics, infection outcomes, and prevention.

As the second largest group of persons to have been infected with human immunodeficiency virus (HIV), and the most likely to transmit HIV to heterosexual partners in the United States and Europe, iv drug users will play an increasingly important role in the future of the AIDS epidemic. This paper reviews five emerging critical issues regarding HIV infection among iv drug users. In epidemiology, rates of drug injection and anonymous sharing of injection equipment appear related to rapid spread of HIV among iv drug users, while heterosexual transmission from iv drug users appears to have been occurring at a relatively slow but constant rate. Data exist that support a gender-related cofactor and a continuing drug injection cofactor, but mechanisms for these potential cofactors have not been determined. Besides frank AIDS, HIV infection also appears to lead to epidemic-level increases in a variety of fatal infections among iv drug users. Several studies of prevention show active risk reduction among iv drug users, but new methods are urgently needed to increase amount of risk reduction.