A 12-year hospital-based surveillance of syphilis in Hanzhong, China: shifting epidemics and implications for targeted prevention

Syphilis remains a global public health priority. China has implemented a national control plan, yet local epidemic dynamics in resource-limited areas are poorly documented. This study aimed to analyze the 12-year trends and population-specific characteristics of syphilis in Hanzhong, China, to inform targeted prevention strategies. We conducted a retrospective analysis of 561,718 syphilis tests performed at Hanzhong Central Hospital from 2012 to 2023. Case positivity was determined according to national diagnostic criteria (non-treponemal and treponemal tests). We calculated annual positivity rates and analyzed trends by sex and age using χ² and trend χ² tests. Among 561,718 tests, 36,913 were positive (overall positivity rate: 6.57%). The positivity rate followed a statistically significant “rise-peak-decline” trend (P < 0.001), peaking at 9.47% in 2020 and decreasing to 5.19% in 2023. While the overall rate was higher among females than males (6.64% vs. 6.48%, P < 0.05), the male rate surpassed the female rate by 2023 (5.63% vs. 4.86%). Adults aged ≥ 60 years had the highest overall rate (9.05%). Neonates (aged 0 ~ 1 year) experienced alarmingly high rates, peaking at 36.24% in 2021 before declining to 17.60% in 2023. Neonates (0 ~ 1 year) had the highest overall positivity rate (15.36%), peaking at 36.24% in 2021 before declining to 17.60% in 2023. Adults aged ≥ 60 years had the second-highest overall rate (9.05%). The syphilis epidemic in Hanzhong has undergone dynamic shifts between 2012 and 2023, with a recent overall decline masking significant subpopulation disparities. Findings highlight a rising burden among men, a persistently high burden among older adults, and critical gaps in preventing mother-to-child transmission. Moving beyond generalized approaches to implement targeted interventions for the identified high-risk groups is essential for syphilis control in this and similar settings.