HIV Molecular Transmission Networks Among MSM in Ningxia, China(2018–2024): Unraveling the Dynamics of an MSM-Driven HIV Epidemic

Background HIV/AIDS among men who have sex with men (MSM) remains a global public health concern, with persistently high infection and incidence rates in this population. This study investigated HIV-1 molecular transmission networks among MSM in Ningxia, China, aiming to characterize transmission dynamics within this population. Methods Plasma samples were collected from sexually transmitted HIV/AIDS patients in Ningxia between 2018 and 2024. HIV-1 RNA was extracted and sequenced for genotyping and drug resistance analysis. Genetic distances were calculated using the TN93 model in HyPhy 2.2.4 (threshold = 1.25%), and molecular transmission networks were visualized in Cytoscape 3.7.0. Bayesian phylogenetic analysis was used to identify migration events, while multivariable logistic regression assessed factors associated with clustering and high linkage. Results Among 296 MSM with successful sequencing, CRF07_BC was the predominant subtype (57.09%), followed by CRF01_AE (20.61%) and CRF55_01B (5.07%), with 2.70% classified as unique recombinant forms (URFs). A total of 129 MSM living with HIV-1 were part of molecular transmission clusters, representing an overall clustering rate of 43.6% (129/296). Transmission network analysis revealed high clustering rates, especially among MSM aged 30–39 (34.1%), primarily within large clusters. CRF07_BC played a dominant role in ongoing local transmission dynamics. Geographically, the majority of clustered cases were from Yinchuan (57.4%), and the strongest connection intensity was observed within Yinchuan, followed by between Yinchuan and Wuzhong. The most robust connections were among MSM aged 25–39. The basic reproduction number (R₀) analysis indicated that the CRF01_AE subtype remained stable, while CRF07_BC showed an increasing trend since 2020, and other subtypes rose sharply after 2022, reflecting subtype-specific differences in transmission dynamics. Among MSM, older age, employment as a worker, and infection with the CRF07_BC subtype were significantly associated with a higher likelihood of clustering in the HIV-1 molecular transmission network. Conclusions MSM aged 25–39 play a central role in HIV-1 transmission among youths in Ningxia, especially those with long-term infections. Addressing transmitted drug resistance among MSM requires immediate action.Targeted screening and intervention strategies are essential to identify and treat high-risk individuals early and reduce onward transmission in this key population.