In the context of HIV transmission through social and sexual networks, debate remains as to the relative contributions from individuals who are either recently or acutely (hereafter, simply “recently”) HIV infected and individuals who have long-term infections. On the one hand, those who are recently infected are more likely to transmit the disease during unprotected sexual intercourse, while on the other hand, there are simply a greater number of long-term infected individuals in the population, a large percentage of whom are not virally suppressed. For a study published in the Journal of Acquired Immune Deficiency Syndromes, my colleagues and I sought to develop a better understanding of the relationship between new HIV seroconversions occurring among young black men who have sex with men (YBMSM) and network proximity to recently or long-term HIV infected individuals.

To this end, we used a cohort of YBMSM from Chicago. A recent HIV infection was defined as either: 1) a confirmed seroconversion 9 months or less prior to interview date or 2) a laboratory confirmed acute infection; long-term HIV infected individuals were defined as a diagnosis date 9 months or more prior to interview date. Sample-weighted logistic regression was utilized to examine network proximity of HIV transmission events to HIV-infected individuals in the network.

Within the cohort, 55.5% of participants were identified as HIV seronegative at baseline. Of these, 9.6% seroconverted during the study period. Those participants whose networks were comprised of a greater number of recently HIV-infected individuals were more likely to seroconvert during the study period, regardless of the number of long-term HIV infected individuals in their network. Importantly, for each network member who was currently taking pre-exposure prophylaxis (PrEP), we also observed a significant 56.0% reduction in the likelihood of seroconversion.

These results suggest that early diagnosis and treatment are critical first steps in preventing further spread of HIV through young MSM. Further, physicians should continue to assess participation in HIV risk behaviors associated with acquisition of HIV and, if warranted, prescribe PrEP.