A Study of Gastroenteritis Outbreak in Hamadan District, Iran: A Case-Control Study

Background and Objectives: Water and foodborne diseases are major causes of mortality worldwide. The aim of this study was to investigate the factors affecting an gastroenteritis outbreak in Hamadan county in summer of 2019.   Methods: This study was performed based on the outbreak investigation process. After producing hypotheses based on preliminary field studies, a case-control study was conducted on 45 cases and 45 controls to investigate the factors associated with the outbreak. New cases of the disease were included according to the case definition. A logistic regression model was used to investigate potential risk factors.   Results: A total of 171 people were affected in this outbreak from 25 June 2019 to 01 July 2019. The at-risk population in this outbreak was 3410 individuals. The attack rate was 5.1%. Abdominal pain, vomiting, and nausea were the most common symptoms with a prevalence of 77.8%, 73.3% and 68.9%, respectively. The results of the case-control study showed that the consumption of tap and spring/well water increased the odds of disease by 4.63 and 4.13 times compared to boiled water, although these relationships were not statistically significant. The odds of diseases were significantly lower in people aged 30-45 years and 46-85 years compared people aged 15 years old and younger.   Conclusion: Based on the results of this study, the outbreak was related to contaminated water consumption. Therefore, regular monitoring of drinking water status is very important for the local health system.