in this country. Our review of HIV infection rates among population subgroups of injection drug users (Chapter 1) indicates wide variation in geographic distribution of HIV infection. Likewise, there is considerable geographic diversity in patterns of injection drug use (e.g., drug used, frequency of injection) (see Chapter 2). The risk of transmission in a population depends on the reservoir of infection (as measured by HIV and other blood-borne pathogen seroprevalence) and the levels of risk behaviors that transmit infection. As these two parameters evolve, so does the epidemic. In order to minimize the occurrence of new infections, ongoing monitoring systems of HIV seroprevalence, seroincidence, and levels of risk behaviors can help guide interventions aimed at curbing new infections. The documented connection between injection drug use and AIDS points to the need to better understand the underlying dynamics of sexual/drug-use behaviors of high-risk groups, and how these networks are linked to other social networks within the intravenous drug user populations. Such an understanding could benefit from the development of theoretical research and alternative methodologies for studying such sensitive topic areas as drug-use and sexual behavior. To better achieve this goal, future research should include the following:
Ongoing coordinated studies are needed of the seroprevalence and seroincidence of HIV, HBV (hepatitis B virus), and HCV (hepatitis C virus) among local populations of injection drug users, using standardized methodologies across locations.
Extensive and repeated surveys of seropositivity rates are needed to determine the incidence and prevalence of infection by age, race/ethnicity, geographic area, and sex. Such studies should be performed locally with standardized protocols developed to ensure comparability of the collected data.
Improved estimation procedures (including enhanced surveillance systems, modeling techniques, and ethnographic methods) should be developed for obtaining more accurate and time-relevant estimates of the number of drug users by city/county rather than attempting to obtain accurate national estimates. Detailed surveys that allow better characterization of specific drug-use behaviors and dynamics of drug-use patterns are needed. This will enable better-targeted prevention efforts.
Developing a typology/demography of HIV infection that identifies high-risk groups in terms of prevalence and incidence and of risk behaviors is necessary to prevent the creation of potential epicenters. Attention should also be given to identifying subgroups or clusters within the broader defined risk groups—e.g., whether there are identificable groups at relatively different levels of risk within the population of local injection drug users. Delineating the characteristics of these subgroups of injection drug users