Transmission Network and Phylogenetic Analysis Highlight the Role of Suburban Population in HIV-1 Transmission Among Older Adults in Nanjing, Jiangsu Province, China.

Describing the transmission characteristics among older adults is essential for designing tailored interventions. An epidemiological investigation combined with phylogenetic analysis was conducted to reveal potential transmission linkages among older adults in Nanjing. Between 2018 and 2022, 188 pol sequences were successfully amplified. Multiple genotypes were identified, including CRF07_BC (55.3%), CRF01_AE (30.3%), CRF08_BC (8.0%), B (3.2%), CRF55_01B (1.1%), CRF67_01B (0.5%), CRF68_01B (0.5%), and unique recombinant forms (URF) (1.1%). Transmission network analysis identified 120 genetically linked patients forming 23 clusters, ranging from 2 to 26 individuals. Multivariable logistic regression analysis showed that compared with farmers and heterosexuals, patients with other occupations (OR = 0.404, 95% CI: 0.173-0.945) and MSM (OR = 0.193, 95% CI: 0.050-0.738) were less likely to have high linkage. Subjects who lived in suburban areas were more likely to have high linkage (OR = 10.932, 95% CI: 3.335-35.830). The Sankey diagram suggested that patients living in suburban areas primarily transmitted the disease within the local district (χ2 = 24.192, p < 0.001). Among the 188 pol sequences, the prevalence of pretreatment drug resistance was 8%. In suburban areas with a rising HIV-1 epidemic, improving early detection and timely treatment is critical. More tailored interventions for this subgroup are urgently needed.