Sociometric risk networks and risk for HIV infection

Objectives. This study examined whether networks of drug-injecting and sexual relationships among drug injectors are associated with individual human immunodeficiency virus (HIV) serostatus and with behavioral likelihood of future infection. Methods. A cross-sectional survey of 767 drug injectors in New York City was performed with chain-referral and linking procedures to measure large-scale (sociometric) risk networks. Graph-theoretic algebraic techniques were used to detect 92 connected components (drug injectors linked to each other directly or through others) and a 105-member 2-core within a large connected component of 230 members. Results. Drug injectors in the 2-core of the large component were more likely than others to be infected with HN. Seronegative 2-core members engaged in a wide range of high-risk behaviors, including engaging in risk behaviors with infected drug injectors. Conclusions. Sociometric risk networks seem to be pathways along which HIV travels in drug-injecting peer groups. The cores of large components can be centers of highrisk behaviors and can become pockets of HIV infection. Preventing HIV from reaching the cores of large components may be crucial in pre venting widespread MV epidemics.