Objective  To understand the causes, infection sources, and transmission routes of two suspected foodborne disease outbreaks in July 2025 in district A and B in Taiyuan, Shanxi province, and provide evidence for precise foodborne disease prevention and control.

Methods Descriptive epidemiology method was used to analyze the clinical characteristics, epidemiological characteristics and related risk factors of the cases. Case-control study was conducted to identify the suspicious food. Food hygiene investigation was carried out to find out the key contamination risks of the suspicious food. Environmental, food and biological samples were collected and tested for relevant pathogens. Whole-genome sequencing was performed for the isolated strains, and pathogen tracing analysis was conducted through core genome multilocus sequence typing (cgMLST) and cluster analysis.

Results A total of 376 people were exposed, with 49 cases were infected, the attack rate was 13.03%. The main clinical manifestations of the cases were diarrhea (95.92%), fever (79.59%), vomiting (44.90%) and abdominal pain (42.86%). Eating durian mille-feuille cake was the risk factor (OR=35.21, 95% CI: 9.37−132.26, P<0.001). Food hygiene investigation found that the cake store manager used private car to transport raw materials and semi-finished products, and the car had no cleaning and disinfection records, indicating a cross-contamination risk. Salmonella Enteritidis was isolated from the processing table, refrigerator, semi-finished products, finished products of the cake store, as well as the stool samples from the store staff and the cases. The core gene difference among the strains was ≤2 alleles (matching rate ≥92%), suggesting that they belonged to the same clonal complex. Clinical case strains, food and environmental isolates were highly clustered in the phylogenetic tree, and strains from different sources shared high genetic homology.

Conclusion This was a foodborne disease outbreak due to the spread of pathogen to end products caused by potential source contamination in transportation and irregular processing in district A and B. It is suggested for cake chain stores to establish a strict supplier audit and invoice/certificate verification system, strictly implement basic hygiene standards such as separation of raw and cooked foods, and prohibit the use of non-specialized vehicle for the transportation of raw materials/semi-finished products of the foods.