An exploratory transmission mode of HIV/AIDS among older people based on data from multiple sources in China.

The HIV/AIDS cases and proportion in older people are continuously and rapidly increasing in China, especially in males. However, the transmission mechanism is not well understood. This study aims to explore the transmission mechanism of HIV/AIDS and potential ways to prevent or control HIV/AIDS transmission in a city in southwestern China. Data from multiple sources, including HIV/AIDS case reports in 2010-2020, a survey of HIV/AIDS cases in 2020, and sentinel surveillance data of female sex workers (FSWs) in 2016-2020 were analyzed. We explored the transmission mechanism of HIV/AIDS cases aged 50 years and older. In this city, the number of newly reported HIV/AIDS cases aged 50 years and older increased from 2010 to 2019, and decreased in 2020. The number of male and female cases aged 50 years and older both increased rapidly in 2017-2019, though the number of male cases was larger than that of female. The survey data showed that 84.7% of older male cases reported commercial sexual behavior, among whom 87.7% reported never using condom and 37.6% reported more than 10 times of commercial sexual behaviors in 1 year. In terms of price of sexual behavior, 68.3% of older male cases sought low-tier FSWs among whom the HIV/AIDS positive rate was 5.4% from the sentinel surveillance data. These results suggested HIV transmission between older men and low-tier FSWs through commercial sexual behavior. Among female cases aged 50 years and older, most reported non-marital and non-commercial heterosexual (60.5%) or regular sexual partner (31.4%) transmission, suggesting that they were infected by their spouse/regular sexual partner. Data of matched couples showed that most male cases had both marital sexual behavior and commercial sexual behavior, or acquired HIV through commercial sexual behavior, while most female cases had only marital sexual behavior. Based on these findings, we proposed a transmission mode of that local older male people and FSWs are transmitting bilaterally through commercial sexual behavior, and local older male people are spreading to local older female people through spouse or regular sexual partner route. By studying data from multiple sources, we explored the HIV transmission mode among older people. In the meantime, we found that marital status had a different impact on male and female old people in their sex behaviors.