An approach to quantifying the interaction between behavioral and transmission clusters. Viruses
Groups of individuals with similar sexual risk behavior have been identified previously in people living with HIV and incident hepatitis C virus (HCV) infection. In addition, phylogenetic analyses have confirmed the presence of HCV transmission networks. However, little is known about the interplay of sexual risk behavior and the conformation of transmission networks.
In this proof-of-concept study, Salazar-Vizcaya et al. aimed to quantify the relationship between behavioral and transmission clusters in people living with HIV and incident HCV infection in the Swiss HIV Cohort Study. The authors used hierarchical clustering algorithms to identify individuals with similar condom use for anal intercourse with unsteady partners (behavioral cluster), and used maximum-likelihood phylogenetic trees of the HCV virus to identify transmission networks (transmission cluster). Membership of behavioral and transmission clusters for were then combined for each patient, and Monte Carlo simulation was used to quantify the strength of the interaction between them.
The study included 36 men who have sex with men and were part of an HCV transmission cluster. Five distinct behavioral clusters were identified and subsequently combined with the information on the HCV transmission cluster. The authors identified interactions between behavioral and transmission groups that were non-random, suggesting some influence of risk behavior on the conformation of transmission clusters. However, the study was not powered to confirm statistical significance.
In summary, the present study outlines a useful approach to characterize associations between clusters of behavior and clusters of transmission. Such analyses could be applied to other infections including HIV or COVID-19 with large transmission networks and increased power. Future studies using this approach may prove useful to complement and guide public health interventions to limit transmission.