Prevalence and influencing factors of HIV/HCV co-infection among drug users in southwest China, 2011-2024

Background: The highest human immunodeficiency virus (HIV) and hepatitis C virus (HCV) prevalence rates are in southwest China. Yunnan Province, located at the southwestern border of China, plays a crucial role in preventing and controlling HIV and HCV. Reports on HIV and HCV co-infection among drug users (DUs) in Yunnan Province are relatively scarce. We conducted a consecutive cross-sectional study to monitor the prevalence of HIV and HCV among DUs over a 15-year period, aimed at describing epidemiological trends in HIV, HCV and co-infection prevalence, and further analyzed influencing factors. Methods: A total of 67,627 DUs were recruited annually from 2011--2024 through compulsory drug rehabilitation centers by cluster sampling from April to July each year in Yunnan, China. HIV and HCV prevalence trends were discussed in terms of the annual percentage change (APC) and average annual percentage change (AAPC). The factors influencing HIV/HCV co-infection were analyzed by logistic regression. Result s: Between 2011 and 2024, the anti-HIV positive rate among DUs decreased from 15.64% to 9.56% (AAPC, -3.806; 95% CI , -7.929~-0.492; P=0.034). The positivity rate of anti-HCV decreased from 50.49% to 25.54% (AAPC, -5.235; 95% CI , -6.740~-2.965; P<0.001). The co-infection rate of HIV and HCV varied from 12.22% to 7.73% between 2011 and 2024 (AAPC, -1.811; 95% CI , -7.943~1.584; P=0.281). From 2011 to 2022, the HIV/HCV co-infection rate significantly decreased from 12.22% to 3.73% (APC, -8.990; 95% CI , -24.986~ -3.9212; P=0.028). The related factors associated with HIV/HCV co-infection included female (OR: 1.82; 95% CI , 1.55~2.12; P<0.001), being born between 1960-1969 (OR _: 2.90; 95% CI , 2.61~3.23; P<0.001), and 1970-1979 (OR, 3.28; 95% CI , 3.05~3.52; P<0.001); primary school and illiteracy (OR _, 1.33; 95% CI , 1.20~1.47; P<0.001), junior high school (OR, 1.12; 95% CI , 1.01~1.23, P<0.001); being unmarried (OR, 1.84; 95% CI , 1.70~1.99; P<0.001); being divorced or widowed (OR _, 1.43; 95% CI, 1.31~1.56; P<0.001); using traditional drugs (OR, 2.54; 95% CI , 2.16~3.00; P<0.001); and engaging in injecting drug use(OR, 6.82; 95% CI , 6.26~7.42; P <0.001). Conclusions: A downward trend in the prevalence of HIV, HCV and co-infection, as well as injecting drug behavior among DUs in Yunnan, is observed in the context of increasing uptake of protective services and behaviors. However, theprevalence of HIV and HCV in China remains notably high. It is particularly crucial to pay attention to those DUs who was born during 1960 to 1970, had a lower education background, were without a spouse, used traditional drugs and hadused injectable drugs ever before. To reducethe threat of HIV and HCV to public health, antiretroviral therapy (ART) should be initiated immediately and incorporated into the follow-up management mechanism among people living with HIV (PLWHs) and HCV RNA-positive individuals.