Investigation of a food poisoning outbreak at a health station, Udon Thani Province, June 2026

Abstract

Background: On June 19, 2026, the Division of Epidemiology received a report from the Office of Disease Prevention and Control Region 8, Udon Thani (ODPC8), that 27 suspected food poisoning cases had been identified as a cluster and were admitted to Prachaksinlapakom Hospital. Most were participants in a meeting held at a health-promoting hospital on June 18, 2026. From June 22-24, 2026, the outbreak investigation and control team from the ODPC8 conducted a field investigation to confirm the diagnosis of food poisoning and the outbreak, describe the characteristics and distribution of the disease by person, time, and place, identify the causes and risk factors for illness, and establish appropriate disease prevention and control measures.

Methods: A descriptive study reviewed medical records and identified additional cases using a standard investigation form. A suspected case was a meeting attendee, or a person living with an attendee, who developed abdominal pain, diarrhea, or vomiting between June 18 and 24, 2026. An analytical epidemiological study using a retrospective cohort study design was conducted to identify risk factors for disease occurrence. Specimens from patients, food handlers, suspected food and water, and kitchen equipment were cultured for enteric pathogens and tested for S. aureus enterotoxin genes. An environmental survey covered food preparation and storage.

Results: The outbreak was a common-source outbreak. Among the 97 people interviewed, 32 met the case definition and were classified as suspected cases, with no confirmed cases. The overall attack rate was 32.99%. Most patients experienced abdominal pain (87.50%), diarrhea (81.25%), and vomiting (75.00%), respectively. The mean incubation period was 4 hours and 45 minutes. Consumption of chicken with rice was associated with illness (RR=108.91, 95% CI 6.87-1726.5, p = 0.0009). However, none of the individual components of the meal was significantly associated with illness. No pathogens were detected in patient specimens, but S. aureus carrying genes encoding enterotoxins A, B, C, D, and E was detected in rice, chicken, and cucumber, and B. cereus was detected from hand swabs of food handlers. An assessment of food preparation procedures and an environmental survey found poor hygiene practices.

Conclusions and discussions: This food poisoning outbreak was caused by S. aureus carrying genes that regulate the production of staphylococcal enterotoxins and B. cereus. The major risk factors were the personal hygiene of food handlers, the cleanliness and standards of food preparation premises, and proper food storage for an appropriate period before consumption. Therefore, restaurant operators should comply with food sanitation standards in accordance with ministerial regulations and notifications of the Ministry of Public Health.