An Outbreak of Gastroenteritis among students of a religious boarding school, district Islamabad: A Retrospective Cohort Study.

Background: On 1 March, 2018, 15 students of a religious boarding school presented to a tertiary care hospital in Islamabad with complaints of nausea, vomiting, abdominal pain and diarrhea. A team of FELTP fellows were tasked to investigate the suspected outbreak to confirm diagnosis, determine magnitude, evaluate possible risk factors, identify the source and implement control measures.  Methods: A retrospective cohort study was conducted from 25 February to 5 March, 2018. Medical records were reviewed at the hospital. All the students and staff of the boarding school were interviewed using a structured questionnaire. A case was defined as any student of the religious school reported with nausea, abdominal discomfort and one of the following symptoms of vomiting, diarrhea, and chills on 1 March, 2018. Information on demographics, history of food intake and clinical features was collected. Suspected food items and drinking water samples were sent to the National Institute of Health for microbiological analysis. Frequencies and attack rates were calculated and risk ratios computed at 95% confidence interval at the margin of error P Results: Out of a total of 120 students, 39.1% (n=47) developed symptoms with an overall attack rate (AR) of 39%. All the students were male with a mean age of 11 years (range 8-14 years). The most affected age group was 10 -11 years (AR 62%). The highest food specific attack rate (82%) was calculated for rice. Among all food items served at breakfast, rice was found statistically significant. Out of 57 students who ate rice, 47 developed illness (RR=17.31, 95% CI 5.70-52.58). During interviews with staff it was found that the food was cooked a day before and stored before being donated to the school by a local restaurant. Staphylococcus aureus was isolated from rice samples.  Conclusion: Consumption of contaminated rice was the most probable cause of the outbreak. Unhygienic storage and handling lead to contamination of the rice. Proper training of food handlers can prevent the transmission of food borne disease. It is strongly recommended that extreme care should be taken while accepting food items from the locals as donation and it should be ascertained that food is not old or smelly. Food must also be accepted with the identity of the person who donates food and this was adopted as a policy later on. In addition to the internal food safety checks, implementation of frequent hand washing and hygiene promotion operating procedures were recommended for the restaurant. Further, an awareness session was conducted on spot among the students and staff.