A simulation model of the dynamics of HIV transmission in intravenous drug users

The complex dynamics of HIV transmission and subsequent progression to AIDS make the use of traditional mathematical modeling techniques problematic. In a previous paper for this journal, Leslie and Brunham established the utility of a nonmathematical simulation language in modeling HIV transfer under conditions similar to those found among homosexual males. This study considers the application of such an approach in modeling HIV spread among intravenous drug users (IDUs) injecting within a "shooting gallery," a location providing a common needle supply to a large number of users. Modeling HIV transmission in this population involves not only consideration of heterogeneity in partnership selection, but also of the fact that spread of the virus is not directly from person to person, but via injection equipment. The General Purpose Simulation System was used to create a hypothetical cohort of IDUs, drawing from a common needle supply. Following introduction of an index case, the HIV infection rate in this cohort was followed over 5 simulated years. The model was then used to consider the effects of systematic variation in the frequency of injection and needle-cleaning behavior.