Pretreatment drug resistance profiles and transmission dynamics of HIV-1 among adults aged ≥50 in Hebei Province, China

Background: In China, the proportion of HIV-infected individuals aged ≥50 is rapidly increasing, yet limited research has focused on HIV transmission dynamics in this population. We investigated pretreatment drug resistance (PDR) and molecular transmission networks among older adults with HIV-1 in Hebei Province. Methods: gene sequencing was performed, with drug resistance mutations and phenotypes determined via the Stanford HIV Drug Resistance Database. A molecular transmission network was constructed using a 1.5% genetic distance threshold. Results: The participants were predominantly male (80.2%), with contact between men who have sex with men (MSM) as the main transmission route (65.3%). CRF07_BC (42.5%) and CRF01_AE (38.0%) were dominant. The overall PDR prevalence was 12.3%, with non-nucleoside reverse transcriptase inhibitor (NNRTI) resistance being the most common (6.6%). The clustering rate was 35.0%. Multivariate analysis identified divorced/widowed status (adjusted odds ratio [aOR] = 2.040), residence in Eastern Hebei (aOR = 2.401), and CRF07_BC infection as independent risk factors for cluster inclusion. Notably, 77.8% of the participants were married, indicating potential spousal transmission through bisexual behavior. Conclusion: MSM is the predominant transmission route among older adults in Hebei. Marital dissolution drives active transmission cluster involvement, while the high proportion of married individuals underscores spousal transmission risk. Given the high PDR prevalence and specific vulnerabilities of older adults, transitioning to integrase strand transfer inhibitor (INSTI)-based regimens and targeted spousal interventions are urgent priorities.