Abstract: Objective To investigate the cause of an outbreak of infectious diarrhea in a town of Meizhou City and propose countermeasures for control of the outbreak.Methods We screened the cases according to the case definition, described the epidemiological characteristics, investigated the habits of drinking water and eating meals, and analyzed the possible exposure factors by carrying out retrospective cohort study.Then we collected clinical specimens, including stool specimens, rectal swabs, and vomitus of part patients, and water samples from waterworks including source water, finished water and tap water, mountain spring, and wells for microbiological and etiological detection.Results From October 20 to 28 in 2012, a total of 131 patients with infectious diarrhea were found in the town, with an attack rate of 0.7%（131/18 597）.The initial case occurred at 23∶00 pm on October 20, and the peak occurred from October 21 to 22, accounting for 80.2% (105/131) of total cases .The main clinical symptoms were vomiting and diarrhea.The gender ratio was 0.7∶1, and the main occupations were farmers (38.9%), students (23.7%), and scattered children (14.5%).13 villages were involved, and the top five villages in incidence were A (30 cases, attack rate 2.7%), B (24, 0.8%), C (21, 1.3%), D (18, 1.4%), and E (10, 1.5%).88.5% (116/131) cases used centralized water supply.The attack rate in eight villages with centralized water supply (1.0%, 116/11 135) was higher than that in villages only using decentralized water supply (0.2%,15/7 462), and the relative risk (RR) was 5.2 (95%CI: 3.0-8.9).There were three waterworks in the town.The X waterworks provided water supply for 6 villages of A, B, C, D, E, and H, where the attack rate was 1.3%（106/8 166）.Y and Z waterworks only supplied their own villages, where the attack rates were 0.4%（9/2 149） and 0.1%（1/820）, respectively.The results of retrospective cohort study indicated that using water from the X waterworks was a risk factor (RR=6.5, 95%CI:3.8-11.1).A total of 12 clinical specimens and 15 water samples were tested.8 clinical specimens, including 2 stool specimens, 5 rectal swabs, and 1 vomitus were positive for Norovirus nucleic acid, 8 water samples from X waterworks, including 1 source water,2 finished water and 5 tap water from pipe network were positive for total coliform group and thermotolerant coliform bacteria, and 7 water samples from X waterworks, including 1 finished water, 3 tap water from pipe network and 3 source water, and 1 well water were negative for Norovirus nucleic acid.