Epidemiological Characteristics and Influencing Factors of Bacillary Dysentery Outbreaks - China, 2008-2024

The incidence of bacillary dysentery (BD) has declined significantly in China, yet BD outbreaks persist across multiple regions. This study describes the epidemiological characteristics of BD outbreaks nationwide and proposes targeted interventions for outbreak prevention and control.

This study obtained BD outbreak data from the Public Health Emergency Event Surveillance System in China for descriptive epidemiological analysis and employed unconditional logistic regression to identify factors influencing outbreak magnitude.

During 2008-2024, China reported 176 BD outbreaks involving 9,854 cases and four deaths. The median attack rate and interquartile range for outbreaks were 5.99% (2.53%, 13.32%). Annual outbreak reports decreased throughout the study period, with no outbreaks documented in 2023 and 2024. Among all outbreaks, 75.6% occurred in rural areas, and 76.7% were reported in schools. Most outbreaks occurred during September or October (52.3%). Shigella sonnei and Shigella flexneri were the predominant outbreak pathogens; the principal transmission routes were waterborne (47.7%) and foodborne (23.9%). Median and interquartile ranges for response times and case counts were 3 (2, 6) days and 44 (25, 71) cases, respectively. Factors associated with larger outbreak size included S. sonnei as the causative pathogen, waterborne transmission, and outbreak duration of eight days or longer.

In China, BD outbreak frequency has decreased substantially. September and October represent high-risk months, with schools serving as the primary outbreak setting during the back-to-school season. Strengthening BD prevention and control in educational institutions, with particular attention to water and food hygiene, remains essential for outbreak prevention.