Epidemiological trend analysis of syphilis in Guangzhou from 2004 to 2023 using Joinpoint regression model

[Objective] To examine the epidemiological trends and characteristics of syphilis in Guangzhou city and provide evidence for the development of effective prevention and control strategies. [Methods] Syphilis case data from Guangzhou, from 2004 to 2023, were collected through the infectious disease surveillance module of the China Disease Control and Prevention Information System (CDCIS). A Joinpoint regression model was applied for time trend analysis, calculating the annual percentage change (APC) and average annual percentage change (AAPC). [Results] From 2004 to 2023, the overall reported incidence of syphilis in Guangzhou increased from 19.25/100 000 to 63.22/100 000 (AAPC=6.23%, P<0.001), while the reported incidence of early-stage syphilis declined from 12.46/100 000 to 6.73/100 000 (AAPC=-2.07%, P=0.116). The incidence of third-stage syphilis rose from 0.13/100 000 to 0.21/100 000 (AAPC=1.77%, P=0.343), whereas fetal syphilis decreased sharply from 0.97/100 000 to 0.02/100 000 (AAPC=-23.03%, P<0.001). Additionally, the incidence of occult syphilis increased significantly from 5.70/100 000 to 56.26/100 000 (AAPC=12.58%, P<0.001). For males, the incidence rose from 23.79/100 000 to 67.74/100 000 (AAPC=5.03%, P<0.001), while in females it increased from 21.28/100 000 to 58.22/100 000 (AAPC=5.06%, P<0.001). The highest annual increase was observed in the 10-19 age group (AAPC=17.23%, P<0.001). Furthermore, the AAPC for reported syphilis incidence in central and peripheral urban areas were 6.33% (Z=4.24, P<0.001) and 7.03% (Z=7.32, P<0.001), respectively. [Conclusions] Overall the incidence of syphilis in Guangzhou has increased from 2004 to 2023, but has stabilized in recent years. Rates remain higher than the national average. While primary syphilis and congenital syphilis have declined, latent syphilis continues to increase. Measures should include raising public awareness, addressing the trend of younger infections, and expanding screening among key populations to ensure early detection, standardized treatment, and reporting, thereby controlling the spread of syphilis.