Objective To analyze the characteristics of HIV-1 molecular network and pretreatment drug resistance genes in the middle-aged and elderly people aged ≥50 years in Huzhou City, Zhejiang Province, and to provide an evidence for the prevention and control of AIDS epidemic.

Methods A total of 332 samples from the newly reported and untreated AIDS patients aged ≥50 years in Huzhou City from January 2020 to December 2023 were collected, pol genes were amplified by reverse transcription polymerase chain reaction (RT-PCR) and nested polymerase chain reaction (nest⁃PCR). Phylogenetic trees analyzing the subtypes were constructed, and a molecular network with a gene distance threshold of 1.0% were constructed at the same time. Mutation sites of drug resistance-related genes were identified through the Data Analysis and Detection System of HIV-1 Resistance Gene Detection of Stanford University, USA.

Results Sequence samples of 308 patients were obtained, and 9 genotypes were identified, including CRF07_BCin 172 cases (55.8%), CRF01_AE in 61 cases (19.8%), CRF08_BC in 43 cases (14.0%), CRF85_BC in 9 cases (2.9%), and CRF55_01B in 8 cases (2.6%), subtypeB in 5 cases (1.6%), subtype C in 4 cases (1.3%), CRF67_01B in 3 cases (1.0%), and unique recombination URF01_AE/07_BC in 3 cases (1.0%). When the gene distance threshold was 1.0%, 28 molecular clusters were formed, and 139 cases were connected to the network, with an access rate of 45.0%. The largest transmission cluster C1 contained 44 cases infected with CRF07_BC subtype, all of whom were heterosexually transmitted, and predominantly by males. A total of 30 patients were found to have low-grade or higher drug resistance mutations, and the pretreatment drug resistance rate was 9.7% (30/308). Among them, there were 5 cases (16.7%) of protease inhibitor (PI) related drug resistance mutations, and 26 cases (86.7%) of non-nucleoside reverse transcriptase inhibitors (NNRTI) related drug resistance mutations.

Conclusion CRF07_BC is the subtype with the most clusters among the middle-aged and elderly infected patients aged ≥50 years in Huzhou City. Middle-aged and elderly transmission clusters are formed within the three counties of WX, NX and CX through related activities. Molecular network monitoring on newly reported cases aged ≥50 years in Huzhou City should be strengthened so that the new characteristics of epidemic changes can be detected in time, providing a scientific basis for adjusting AIDS prevention and control measures for the elderly.