Abstract:

Objective To analyze the epidemiological characteristics of syphilis infection in Wuhu City after expanded screening of syphilis in 2015 for evidence to optimize the prevention and control strategies. Methods The data of syphilis cases in Wuhu City maintained from 2015 to 2024 were retrieved through the Chinese Disease Prevention and Control Information System. The epidemiological characteristics were analyzed by descriptive epidemiological method, the Joinpoint regression model was used to analyze the trend of incidence, and the correlation between expanded screening and case report was analyzed as well. Results From 2015 to 2024, the total number of syphilis serological screening in Wuhu City was 2 793 280, and the number of double positive rate was 27 837. A total of 22 688 syphilis cases were reported, with an average annual reported incidence of 60.86/100 000 population. In total, 18 108 cases of latent syphilis (79.81%), 4 348 cases of primary and secondary syphilis (19.16%), 179 cases of tertiary syphilis (0.79%), and 53 cases of congenital syphilis (0.23%) were reported. Cases were reported in each month, without typical seasonal patterns. The number of reported cases were 11 454 for males and 11 234 for females. The average annual reported incidence rates were 60.36/100 000 and 61.38/100 000, respectively. The highest incidence was seen in the age group ≥65 years (110.87/100 000), and the highest number of reported cases were in housewife and unemployed individuals (n=8 531; 37.60%), followed by farmers (n=7 066; 31.14%). The number of reported cases in Jinghu District ranked the first in the city (n=4 226; 18.63%). On the incidence trend, the reported incidence of syphilis as well as primary and secondary syphilis showed a downward trend (AAPC=-1.22%, t=-2.74, P<0.05; AAPC=-20.10%, t=-7.46, P<0.001, respectively), yet latent syphilis showed an upward trend (AAPC=5.90%, t= 3.55, P<0.001). Among different populations, the reported incidence of syphilis in the 15-24 age group showed upward trend in 2017-2024 (APC=10.12%，t=2.61，P<0.05), while the 25-34 age group exhibited a downward trend (AAPC=-10.89%, t=-13.80, P<0.001). The 55-64 age group presented an upward trend in 2015-2021 (APC=4.93%, t=6.64, P<0.05), yet a downward trend in 2021-2024 (APC=-8.54%, t=-4.16, P<0.05). In different regions, the reported incidence of syphilis exhibited a downward trend overall in Yijiang District (AAPC=-7.11%, t=-6.23, P<0.001) and Fanchang District (AAPC=-4.27%, t=-3.21, P<0.05). Although the reported incidence tended to rise in Wanzhi District in 2015-2019 (APC=10.68%, t=3.29, P<0.05), yet showed a downward trend in 2019-2024 (APC=-5.87%, t=-2.77, P<0.05). The number of screening and double-positive was positively correlated with the number of latent syphilis reports (r=0.693, 0.754; both P<0.05), and negatively correlated with the number of primary and secondary syphilis reports (r=-0.976, -0.830; both P<0.05). Conclusion The reported incidence of syphilis in Wuhu area showed a downward trend from 2015 to 2024, with a significant decrease in early active syphilis. The elderly aged 65 and above, homemakers and unemployed individuals, as well as farmers, are key populations for prevention and control. The increase of latent syphilis reports was closely related to expanded screening.

Key words: Syphilis, Epidemiological characteristics, Expand screening, Joinpoint regression model, Correlation analysis, Wuhu City