Work

Gender disparities and stage-dependent HIV transmission in Nanning, China: a dynamic modeling analysis of transmission routes and intervention effectiveness

Year: 2026

Type: article

Abstract: Acquired immunodeficiency syndrome (AIDS) is caused by infection with the human immunodeficiency virus (HIV). Existing dynamic models often lack gender stratification, fail to quantify the contributions of specific transmission routes, and rarely incorporate long-term surveillance data for validation. This study developed a sex-based transmission model using HIV surveillance data from Nanning from 2001 to 2019 to characterize gender-specific transmissibility, identify key transmission routes, and provide evidence for precise, gender-responsive prevention strategies. We constructed a sex-based transmission dynamics model to fit reported HIV data and estimate the transmissibility of different transmission routes. A “knockout” approach was used to identify indispensable transmission routes at different epidemic stages. Model simulations were used to evaluate the effectiveness of potential interventions and inform theoretical intervention strategies. The epidemic exhibited three distinct stages with substantial gender differences. The first stage was characterized by rapid growth, followed by steady growth in the second stage, and stabilization after 2012 in the third stage. Transmission patterns shifted from injection drug use to sexual transmission as the dominant route. Among men, transmission shifted from injection drug use to heterosexual contact, with an increasing contribution from men who have sex with men (MSM) transmission (which reached 14.87% in the third stage). Among women, heterosexual transmission increasingly predominated, accounting for 98% of all transmission. The effective reproduction number gradually declined across the three stages. Female-to-male and MSM transmission were dominant in stage 1; female-to-female transmission emerged as the dominant route in stage 2; all transmission routes had effective reproduction numbers below 1 in stage 3. Knockout simulations indicated that heterosexual transmission was critical in stage 1, female-to-female transmission was most influential in stage 2, and single-route interventions had a limited effect in stage 3. Scenario‑based projections under constant intervention intensity indicated only a slow decline, whereas counterfactual scenarios assuming reduced intervention intensity resulted in explosive epidemic growth. Improving case detection (increasing u from 0.80 to 1.00) achieved near‑complete elimination of new infections, representing the largest relative reduction per unit increase in the detection rate among the strategies evaluated. This study delineates the three-stage evolution of HIV transmission in Nanning using a sex-based transmission dynamic model. The first rapid-growth stage was dominated by heterosexual transmission, highlighting weaknesses in early epidemic control. The second slow-growth stage was driven primarily by female transmission, and expanded testing and targeted interventions helped contain further explosive growth. The third plateau stage indicates that all routes have lost sustained transmission potential. However, the epidemic remains high. Although current interventions can stabilize the epidemic, they are insufficient to substantially reduce the burden, highlighting the need for more refined and integrated prevention strategies.

Source: BMC Public Health

DOI: 10.1186/s12889-026-30219-w