Objective: To identify the cause and mode of transmission of a gastroenteritis outbreak in a village, Henan province.
Methods: Gastroenteritis patients were identified through family visits, interviewing the village doctors and reviewing diagnosis and prescription records at the village health clinic. Cases were defined as onset of one of the four symptoms from the village resident during July 20 to August 12, 2010. The symptoms would include diarrhea (≥ 3 times/day), abdominal pain, nausea or vomiting. A retrospective cohort study was conducted to assess the association between drinking raw well water or eating noodles rinsed by raw well water and gastroenteritis. Stools or vomits of the case-patients and the well water samples were tested for bacterial pathogens.
Results: Data for 60 case-patients were collected. All cases occurred in the northern part of the village. Persons who used water from a public well in the northern part of the village had an attack rate of 55%, which was 3.5 times of those who did not use the well water (16%) (RR = 3.5, 95%CI: 1.2 - 10). Results from the retrospective cohort study showed that drinking un-boiled water from the well was a risk factor (RR = 1.7, 95%CI: 1.3 - 2.3). Laboratory testing showed that total coliform and E. coli both greatly exceeded the limit considered safe for drinking, indicating there was fecal contamination in the well water. No bacterial pathogens were detected in the patients' stools or vomits.
Conclusion: The outbreak was mainly caused by drinking contaminated water from the public well in the northern part of the village.