Foodborne disease outbreak in a primary school for girls—Saudi Arabia, Riyadh, in 2023: A retrospective cohort study

Background: Foodborne illnesses are infectious or toxic caused by organisms or chemical substances through eating contaminated food. The current outbreak of foodborne diseases occurred in a girls' primary school in Riyadh on December 21, 2023. The study aimed to investigate the outbreak and recommend preventive measures to prevent similar outbreaks.

Methods: A retrospective cohort study was conducted in this study. Cases were defined as people who ate during an open day in the primary school for girls and developed any or a combination of the following symptoms: Diarrhoea, vomiting, fever, or abdominal pain within 36 hours of food consumption. We collected information on demographics, symptoms, and food history using a semi-structured questionnaire. We reviewed available laboratory results for cases, retained food items, and conducted an active case search to identify more cases. The data was analyzed using SPSS. Risk ratios and 95% confidence intervals were calculated.

Results: 145 female cases among 259 ate during an open day in the primary school in Riyadh, which indicated an attack rate of 55.98%. Of 145 cases, The ages ranged between 6-40 years. Among cases, 97.93% had abdominal pain, 57.93% had nausea, 23.44% had vomiting, 18.62 developed Diarrhoea, and 4.82% had fever. The incubation period ranged from 45 minutes to 5.5 hours, with a mean of 2.5 hours. Among nine food items consumed, chicken burger (relative risk 1.64, 95% CI 1.35-2), cotton candy (relative risk 1.69, 95% CI 1.4-2.04), balilah (relative risk 1.44, 95% CI 1.06-1.93) and shawarma (relative risk 1.31, 95% CI 1.05-1.64) were significantly associated with illness. Laboratory investigation of food samples (chicken burger, chips and grape leaves) and six rectal swabs were negative. There were no hospitalizations or deaths and all cases were discharged.

Conclusion: Based on the outbreak investigation, there might be some differential diagnosis, but we could not definitively identify the source of the outbreak. The current outbreak could be caused by chemicals or toxins in chicken burger, shawarma, balilah, and cotton candy. Cross-contamination may explain why so many food items were implicated. We recommend increased supervision and periodic examinations for food handlers and more education for food handlers about food safety.

Keywords: Foodborne Disease, Outbreak, Primary School, Retrospective Cohort Study, Food‑Specific Attack Rates.