Spatiotemporal distribution of primary and secondary syphilis in Zhejiang, 2016−2020

  Objective   To analyze the spatiotemporal distribution of primary and secondary syphilis in Zhejiang province from 2016 to 2020, explore the clustering area and provide theoretical basis for the accurate prevention and control of syphilis.

  Methods   The data of primary and secondary s yphilis cases in Zhejiang were collected from China Disease Control and Prevention Information System, and software arcgis 10.8 was used to establish a spatial analysis database for spatial autocorrelation analysis. Software SaTScan 9.7 was used for spatiotemporal scanning analysis.

  Results   In Zhejiang, a total of 33 226 cases of primary and secondary syphilis were reported from 2016 to 2020, with the average incidence rate of 11.65/100 000 (from 2.62/100 000 to 40.40/100 000), and the annual incidence rates showed a decrease trend (χ²=26.136, P<0.001). In terms of the overall spatial distribution, the incidence was higher in eastern area and lower in central area. The global autocorrelation results showed that the incidence of primary and secondary syphilis showed clustering (Moran's I index were all >0, Z values were all >1.96, and P values were all <0.001), and the local autocorrelation analysis showed that there was one high-high clustering area in Jiaojiang, Huangyan, Sanmen and Linhai of Taizhou and 4 low-low clustering areas (Qingtian in Lishui, Lucheng, Ouhai and Rui’an in Wenzhou, Pan’an and Dongyang in Jinhua, Keqiao in Shaoxing, Longyou in Quzhou). The results of local G-statistic hotspot analysis showed that there were 6 ‘positive hotspots’ (Jiaojiang, Huangyan, Luqiao, Tiantai, Sanmen and Linhai of Taizhou) and 5 ‘negative hotspots’ (Lucheng, Ouhai, Rui’an of Wenzhou, Longyou of Quzhou, Shengzhou of Shaoxing) in Zhejiang. Spatiotemporal scanning detected four clustering areas, the most likely clustering and secondary likely clustering were mainly in Taizhou, Ningbo and Zhoushan along the eastern coast.

  Conclusion   The incidence rate of primary and secondary syphilis reported in Zhejiang showed spatial clustering. In the future, syphilis prevention and control in the eastern coastal area of Zhejiang should be strengthened.