Nguyen T, Delaugerre C, Valantin MA, et al. - Hepatitis C virus (HCV) transmission dynamics among HIV-positive and HIV-negative men having sex with men (MSM) was investigated via ultradeep sequencing (UDS). Researchers performed sequencing of NS5B fragment (388 bp) from virus of 50 HIV-positive and 18 HIV-negative patients diagnosed with recent HCV infection. Using Geneious (version 10.3.2), analysis of UDS data was performed. Using FastTree (version 2.1), they constructed phylogenetic trees that were then submitted to ClusterPicker (version 1.2.3) for transmission chain detection at different thresholds of maximum genetic distance (MGD) (3% for Sanger, 3% and 4.5% for UDS). Sanger at 3%, UDS at 3% and at 4.5% of MGD led to the identification of 10, 17, and 18 HCV transmission chains, respectively. They observed involvement of 38 (55.9%), 38 (55.9%), and 43 (65.3%) individuals, among 68 enrolled patients, in transmission networks found by Sanger at 3%, UDS at 3%, and at 4.5% of MGD, respectively. They detected mixed transmission chains including HIV-positive and HIV-negative patients for 8/10 chains by Sanger at 3%, for 9/17 by UDS at 3%, and for 10/18 by UDS at 4.5% of MGD. The analysis thereby suggests that HCV transmission networks are shared by HIV-positive and HIV-negative MSM.