Dennis AM, Volz E, Frost S, Hossain ASMM, Poon AFY, Rebeiro P, Vermund SH, Sterling TR, Kalish ML. HIV-1 transmission clustering and phylodynamics highlight the important role of young men who have sex with men. AIDS research and human retroviruses. 2018 Jul 20. PMID: 30027754 [PubMed]
More persons living with HIV reside in the Southern US than in any other region, yet little is known about HIV molecular epidemiology in the South. We used cluster and phylodynamic analyses to evaluate HIV transmission patterns in middle Tennessee. We performed cross-sectional analyses of HIV-1 pol sequences and clinical data collected from 2001-2015 among persons attending the Vanderbilt Comprehensive Care Clinic. Transmission clusters were identified using maximum likelihood methods and patristic distance differences. Demographic, risk behavior, and clinical factors were assessed evaluating "active" clusters (clusters including sequences sampled 2011-2015) and associations estimated with logistic regression. Transmission risk ratios for MSM were estimated with phylodynamic models. Among 2915 persons (96% subtype-B sequences), 963 (33%) were members of 292 clusters (distance ≤1.5%, size range 2-39). Most clusters (62%, n=690 persons) were active, either being newly identified (n=80) or showing expansion on existing clusters (n=101). Correlates of active clustering among persons with sequences collected 2011-2015 included MSM risk and age ≤30 years. Active clusters were significantly more concentrated in MSM and younger persons than historical clusters. Young MSM (≤26.4 years) had high estimated transmission risk (risk ratio=4.04 [2.85-5.65] relative to older MSM) and were much more likely to transmit to young MSM. In this Tennessee cohort, transmission clusters over time were more concentrated by MSM and younger age, with high transmission risk among and between young MSM, highlighting the importance of interventions among this group. Detecting active clusters could help direct interventions to disrupt ongoing transmission chains.