Objective  To understand the epidemiological characteristics of bacillary dysentery in Tibet autonomous region from 2019 to 2024, identify high-risk areas for the transmission of bacillary dysentery, and provide scientific basis for targeted prevention and control efforts.

Methods The monthly incidence data of bacillary dysentery and reports of public health emergencies in Tibet from 2019 to 2024 were collected from China Disease Prevention and Control Information System and National Public Health Emergency Reporting Information System for a descriptive epidemiological analysis. Joinpoint regression analysis was conducted to evaluate the incidence trend. Spatial autocorrelation and spatiotemporal scanning statistics were used to understand the spatiotemporal distribution of the cases.

Results From 2019 to 2024, a total of 3 896 cases of bacillary dysentery were reported in Tibet without death. The annual average incidence rate was 18.08/100 000. The overall incidence of bacillary dysentery showed a consistent downward trend over years (χ² _trend=699.461, P<0.001). (APC=−22.10%, AAPC=−22.10%, 95%CI: −37.09% to −9.70%, P<0.05). The incidence exhibited distinct seasonal patterns. The annual incidence was high during June - September and peaked in July, with the reported cases accounting for 50.51% (1 968/3 896)of the total. The top three districts and counties with the high average annual reported incidence rates were Qushui County in Lhasa (85.29/100 000), Gongga County (71.74/100 000), and Gangba County in Shigatse (64.98 /100 000). The male to female ratio of the cases was 0.89∶1, the incidence rate was highest in age group <5 years (506.64/100 000). The Moran’s I values for spatial autocorrelation across the years for bacillary dysentery were all positive (all P<0.05). The “high-high” clustering pattern was mainly distributed in the gore area comprising Gongga, Linzhou and Zhanang counties, with Chengguan District at its core. Spatiotemporal analysis showed that the clustering mainly occurred between May and November, with the RR values ranging from 1.64 to 3.63. A total of 4 school outbreaks were reported in the region, three of which were related to drinking water and one to food contamination.

Conclusion In Tibet, the incidence of bacillary dysentery showed a single-peak pattern, mainly occurring between June and September. Home cared children under 5 years old were the population at high-risk. The disease exhibited spatial clustering, and contamination of drinking water and food led to the outbreaks in schools. It is suggested to conduct investigations into the causes of high incidence in high-high clustering areas and strengthen prevention and control in summer and autumn . In addition, improve the supervision of drinking water and food safety in schools to prevent local outbreaks.