Ragonnet-Cronin M, et al. - In view of the observation that undiagnosed infection is common in transgender women despite being at high risk for HIV infection, researchers aimed to identify transgender women and their partners in a molecular transmission network to prioritize public health activities. Since 2006, HIV protease and reverse transcriptase gene (pol) sequences from drug resistance testing have been reported to the Los Angeles County Department of Public Health and linked to demographic data, gender, and HIV transmission risk factor data for each case in the enhanced HIV/AIDS Reporting System. Using HIV-TRAnsmission Cluster Engine (with a pairwise genetic distance threshold of 0·015 substitutions per site) from the earliest pol sequences from 22,398 unique individuals, including 412 (2%) self-identified transgender women, they constructed a molecular transmission network. In the network across 1722 molecular transmission clusters, 8133 (36·3%) of 22,398 individuals were clustered. Recognition of clusters that may possibly include undiagnosed transgender women with HIV and enhancement in targeting of public health prevention and treatment services to transgender women could be done with the potential use of molecular epidemiology as demonstrated by clustering of transgender women and the observed tendency for linkage with cisgender men who did not identify as men who have sex with men (MSM).