Combining molecular transmission network analysis and spatial epidemiology to reveal HIV-1 transmission pattern among the older people in Nanjing, China

Abstract

Background In China, the problem of HIV infection among the older people has become increasingly prominent. This study aimed to analyze the pattern and influencing factors of HIV transmission based on a genomic and spatial epidemiological analysis among this population. Methods A total of 432 older individuals who were newly diagnosed with HIV-1 and had not received ART between January 2018 and December 2021 were enrolled. HIV-1 polgene sequence was obtained by viral RNA extraction and nested PCR. The molecular transmission network was constructed using HIV-TRACE and the spatial distribution analyses were performed in ArcGIS. The multivariate logistic regression analysis was performed to analyze the factors associated with clustering. Results A total of 382 sequences were successfully sequenced, of which CRF07_BC (52.1%), CRF01_AE (32.5%), and CRF08_BC (7.3%) were the main HIV-1 subtypes. A total of 176 sequences entered the molecular network, with a clustering rate of 46.1%. Impressively, the clustering rate among older people infected HIV with commercial heterosexual transmission was as high as 61.7% and three female commercial sex workers were observed in the network. The individuals who were aged ≥ 60 years and transmitted by commercial heterosexual behaviors had a higher risk of clustering, while those who were retirees or engaged other occupations and with higher education degree were less likely to cluster. There was a positive spatial correlation of clustering rate (Global Moran I =0.206, P < 0.001)at the town level and the highly aggregated regions were mainly distributed in rural area. We determined three large clusters and they mainly spread in the intra-region of certain towns in rural areas. Notably, 54.5% of cases in large clusters were transmitted through commercial heterosexual behaviors. Conclusions These findings revealed the spatial aggregation of HIV transmission and highlighted vital role of commercial heterosexual behavior in HIV transmission among older people at the local level. Therefore, health resources should be directed towards highly aggregated rural areas and prevention strategy should take critical regions or persons as entry points. Moreover, continuous monitor and rapid area response to the network should be strengthened to reduce further HIV transmission among older people.