Exploring HIV-1 Transmission Features Among Older Individuals in Developed Eastern China

The number of newly reported HIV-1 infections among older individuals (≥50 years of age) has increased rapidly in Hangzhou, a central city in the Yangtze River Delta region of China. To provide a scientific basis for prevention and intervention strategies targeted at older individuals in Hangzhou, an epidemiological survey combined with molecular transmission network analysis was conducted. A total of 2,899 individuals with newly confirmed HIV-1 infections, including 635 older individuals and 2,264 younger individuals (<50 years of age), were enrolled in this study. Among older individuals, heterosexual contact was the predominant mode of HIV-1 transmission. In addition, it was observed that older individuals with lower levels of education exhibited a higher susceptibility to HIV-1 infection. The analysis of transmission network, which was inferred using HIV-TRACE algorithm, revealed that the newly diagnosed HIV-1 infections among older individuals in Hangzhou exhibited a pattern of scattered transmission, with key clusters primarily located in non-main urban areas. The predominant mode of transmission in these areas was nonmarital and noncommercial or nonmarital and commercial heterosexual transmission. Notably, the study highlighted a significant proportion of older individuals (73.3%, 11/15) within B subtype. Multivariate logistic regression analysis further revealed that the subtype B was a significant factor associated with older individuals having ≥3 node degrees in the network, occurring 5.55 times more frequent than subtype CRF07_BC (95% confidence intervals = 1.17–26.22, p = .031). Furthermore, the lower CD4 levels observed among older individuals underscored the challenge of late diagnosis in Hangzhou. Taken together, it is imperative to test and intervene for high-risk older individuals. To tackle this issue effectively, it is essential to enhance the detection of the B subtype and implement targeted interventions in key clusters within non-main urban areas. In addition, proactive measures should be implemented to address the challenge of late diagnosis in Hangzhou by promoting widespread testing among the older individuals, particularly in priority areas.