Objectives: To identify the etiology and source after recognition of diarrhea outbreak is associated with drinking water in suburb of Chengdu. Methods: Both unmatched case control and retrospective cohort study were conducted. 131 targets including 56 suspected patients were recruited for case control study, while 463 residents were selected for cohort study. Stool, water and environmental samples were collected for laboratory testing. Results: The proportion of case exposed to well water was

more »

... % in case group compared with 51% in the controls during the epidemic period (OR = 6.14, P < 0.01). Exposing to well water (RR = 3.14, P < 0.01) and the distance between well and river (RR = 2.59, P < 0.01) were at higher risk for diarrheal illness. Nucleic acid of Enteropathogenic E. coli and Enterotoxigenic E. coli was positive in stool and river samples. Conclusions: This outbreak of diarrhea might be caused by several mixed opportunistic pathogens in well water contaminated from the river water.