Introduction Research on the HIV vulnerability of men who have sex with men (MSM) in India has tended to focus on aggregates of individual risk behaviours. However, such an approach often overlooks the complexities in the sexual networks that ultimately underpin patterns of spread. This paper analyses a set of sexual contact network (SCN) snapshots in relation to ethnographic findings to reorientate individual-level explanations of risk behaviour in terms of more complex systems.

Methods Fifteen community researchers conducted a 2-month ethnographic study in three cities in Karnataka to generate descriptions of the risk environments inhabited by MSM. SCNs were reconstructed by two methods. First, initial participants, defined as nodes of various sexual networks, were purposively sampled. In each site, six nodes brought in three sexual partners separately as participants. In all sites, 72 participants completed 431 surveys for their 7-day sexual partners. Second, each site determined four groups representing various sexual networks, each group containing four individuals. In all sites, 48 participants completed 334 surveys for their regular sexual partner.

Results Considerable differences were observed between sites for practically all included behavioural variables. On their own, these characteristics yielded contradictory interpretations with respect to understanding contrasts in HIV prevalence at each site. However, viewing these variables in relation to SCNs and ethnographic data produced non-linear interpretations of HIV vulnerability which suggested importance to local interventions.

Conclusion SCN data may be used with existing data on risk behaviour and the structural determinants of vulnerability to re-tailor more tightly focused interventions.