Phylogenetic analysis highlights the role of older people in the transmission of HIV-1 in Fuyang, Anhui Province, China

BACKGROUND: The proportion of older HIV-1 infected people in China has increased rapidly in recent years. Elucidation of the transmission characteristics of this high-risk population subgroup is helpful for the development of tailored interventions. METHODS: A phylogenetic analysis was performed that uses available HIV-1 pol sequences amplified with nested RT-PCR from plasma samples of all newly diagnosed participants spanning from October 2017 to September 2018 in Fuyang, Anhui Province. Transmission clusters were identified as two or more sequences that shared a corresponding node with an aLRT-SH value ≥90 in the maximum-likelihood phylogenetic tree and had an overall mean genetic distance of ≤1.5%. A local transmission cluster was defined as a cluster that had more than 80% of its sequences from Fuyang. The role of older people in local HIV-1 transmission was determined using an integration of molecular and demographic data. RESULTS: Of 362 available sequences, 14 subtypes, and 28 local transmission clusters were identified. It was found that the proportion of older people in the local transmission cluster (69/77, 89.61%) was much higher than that of younger people (46/114, 40.35%) (χ(2) test, P < 0.001). In the pretreatment drug resistance analysis, the proportion of sequences with PDRMs in the local transmission cluster was not significantly different between the older people group (57.14%, 4/7) and non-old-aged group (11.11%, 1/9) (Fisher’s exact test, P > 0.05). CONCLUSION: By combining phylogenetic analyses with demographic data, more detailed information was provided about the local transmission structure in Fuyang. These findings suggested that older people play an important role in local transmission, and more tailored interventions for this population subgroup are urgently needed.