  Social context plays an important role in perpetuating or reducing HIV risk
behaviors. This study analyzed the network and individual attributes that were
associated with the likelihood that people who inject drugs (PWID) will engage
in HIV risk behaviors with one another. We analyze data collected in the Social
Risk Factors and HIV Risk Study (SFHR) and Transmission Reduction Intervention
Project (TRIP) to perform the analysis. Exponential random graph models were
used to determine which attributes were associated with the likelihood of
people engaging in HIV risk behaviors, such as injection behaviors that are
associated with one another, among PWID. Results across all models and across
both data sets indicated that people were more likely to engage in risk
behaviors with others who were similar to them in some way (e.g., were the same
sex, race/ethnicity, living conditions). In both SFHR and TRIP, we explore the
effects of missingness at individual and network levels on the likelihood of
individuals to engage in HIV risk behaviors among PWID. In this study, we found
that known individual-level risk factors, including housing instability and
race/ethnicity, are also important factors in determining the structure of the
observed network among PWID. Future development of interventions should
consider not only individual risk factors, but communities and social
influences leaving individuals vulnerable to HIV risk.
