HIV risk behaviors in African-American drug injector networks: implications of injection-partner mixing and partnership characteristics.

AIMS: We explore the mechanisms by which 'partnership-level' variables--the mix of characteristics of individuals who inject drugs together--affect the incidence of HIV risk behaviors, including receptive syringe sharing, and facilitate or impede the spread of HIV.
DESIGN: We apply multivariate analysis techniques to data on injection partnerships (pairs of individuals who inject drugs together) collected using a network sample of 401 African-American IDUs in Washington, DC.
FINDINGS: Drug injectors tended to select injection partners of the same gender and similar age, but risk behaviors were most common in partnerships between individuals who are dissimilar in both gender and age. Partners who had a sexual relationship, injected drugs frequently together, smoked crack-cocaine regularly, injected speedball (heroin mixed with cocaine) regularly and/or had close social ties were more likely to engage in risky injection practices than otherwise similar partners. These factors account largely for the association between the gender-age mix of the partnership and injection risk behavior.
CONCLUSIONS: Among African-American IDUs in Washington DC, partnership-level variables appear critical in the transmission of HIV.