Divergent Trends of Human Immunodeficiency Virus/Acquired Immunodeficiency Syndrome (HIV/AIDS), Syphilis, and Gonorrhea in China: A National Age-Period-Cohort Analysis, 2006–2020

Huihui Tuo¹Fang Feng²Ronggui Tao³ZhongYu Wang³Shuo Feng¹Luqian Zhang^4*Yan Zheng^1*

• ¹Department of Dermatology, The First Affiliated Hospital of Xi'an Jiaotong University, Xi‘an, China
• ²Department of Gynecology and Obstetrics, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
• ³Department of Urology, The First Affiliated Hospital of Xi’an Jiaotong University, Xi'an, China
• ⁴Shaanxi Provincial Center for Disease Control and Prevention, Xi'an, China

Objective: Sexually transmitted diseases (STDs) remain a significant public health challenge globally and in China. This study analyzes incidence trends of three nationally notifiable STDs to assess their disease burden. Methods: Based on national surveillance data (2006–2020) from the Chinese Center for Disease Control and Prevention, this study analyzed incidence trends of human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS), syphilis, and gonorrhea using Joinpoint regression. Age-period-cohort modeling was subsequently employed to evaluate the independent effects of age, period, and birth cohort. Results: Between 2006 and 2020, China observed a significant increase in the incidence of HIV/AIDS and syphilis (p < 0.001). Although gonorrhea incidence declined overall (p < 0.05), a notable increase was observed among adolescents under 20 years of age (p < 0.001). The average annual reported incidence was highest for syphilis (28.41 per 100,000), followed by gonorrhea (8.65 per 100,000) and HIV/AIDS (2.78 per 100,000). Geographically, HIV/AIDS incidence was highest in southwestern China. Syphilis incidence was elevated in the southwestern, southern, and northwestern regions, while gonorrhea showed a distinct concentration in southern China. Age-effect analysis revealed a bimodal pattern for both HIV/AIDS and syphilis, with incidence peaks in the 20– 39 and ≥60 age groups. In contrast, gonorrhea showed a single peak in the 20–39 age group. Period-effect analysis, using the 2011–2015 period as reference, indicated evolving disease risks in subsequent years: HIV/AIDS risk increased markedly in 2016–2020, syphilis risk increased modestly, while gonorrhea risk initially declined in 2006–2010 before a slight rise in 2016–2020. Cohort analysis showed that HIV/AIDS risk was highest among individuals born in 2011–2015. The peak risk for syphilis occurred in the 2006–2010 birth cohort, while gonorrhea risk was highest in the 1921–1925 birth cohort. Conclusions: HIV/AIDS and syphilis present growing threats in China, disproportionately affecting young adults and the elderly, with increasing burden in recent birth cohorts. Although gonorrhea shows overall decline, its rise in adolescents warrants attention. A tiered prevention strategy is recommended: enhanced screening and education for HIV/syphilis in high-risk groups and regions, alongside sustained gonorrhea surveillance in key populations.