Objective To investigate the epidemiological characteristics and causative agents of a gastroenteritis outbreak at a team-building facility, providing a scientific basis for developing targeted prevention and control measures.

Methods A field epidemiological investigation was conducted regarding a gastroenteritis outbreak that occurred on April 26, 2025, at a team-building facility in Ningbo city. Medical records were reviewed, and on-site interviews and questionnaire surveys were conducted to establish a case definition. According to this definition, cases were identified, and data were collected to describe the epidemiological distribution characteristics of the cases. A case-control study was performed through propensity score matching (PSM) to match 69 cases with 69 controls at a ratio of 1 : 1, and potential causative factors were analyzed. Anal swab samples from cases and restaurant staff, food samples retained for testing, and environmental samples from the kitchen were collected for fluorescence quantitative PCR and bacteria isolation. Whole genome sequencing was performed for the isolates to trace the sources.

Results A total of 525 individuals were involved in the investigation. Seventy cases (including probable and confirmed cases) were identified, with an attack rate of 13.3%. The primary clinical symptoms were diarrhea (100.0%, 70/70) and abdominal pain (65.7%, 46/70), while vomiting was rare (4.3%, 3/70). The epidemic curve showed a point source exposure pattern, with a median incubation period of 14 h (range of 2–26 h). Multivariate logistic regression analysis showed that beer duck (OR = 3.028, 95%CI: 1.331–6.887), stir-fried vegetables (OR = 3.184, 95%CI: 1.461–6.936), and scrambled eggs with tomatoes (OR = 4.160, 95%CI: 1.715–10.089) increased the risk of disease. Laboratory tests found that among the 10 diarrheagenic Escherichia coli (DEC) nucleic acid-positive case samples, enteropathogenic Escherichia coli (EPEC), enteroaggregative E. coli (EAEC), and enterotoxigenic E. coli (ETEC) accounted for 80.0% (8/10), 10.0% (1/10), and 10.0% (1/10), respectively. EPEC nucleic acid was detected in multiple food and environmental samples such as stir-fried vegetables and stir-fried pork. The EPEC strains from the two cases were highly homologous (0 allele difference).

Conclusions This is an outbreak of gastroenteritis caused by polytype DEC (mainly EPEC) contaminating various dishes in the lunch of a team-building facility.