ObjectiveTo investigate the risk factors of a diarrhea outbreak in the first affiliated hospital of X University in Xi'an in 2019 and provide evidence for the outbreak prevention and control.

MethodsCase finding, field epidemiologic and hygienic investigation were conducted, and stool samples or anal swabs, vomitus of patients, and water samples and environmental surface swabs in the hospital were collected. RT-PCR was performed for pathogen identification.

ResultsA total of 22 cases of diarrhea were reported in 169 inpatients, family members and hospital staff. The attack rate was 13.02%. The main clinical manifestations were diarrhea, abdominal distension and vomiting. The attack rate in inpatients was higher than that in their family member ( χ² =16.341, P<0.01). The attack rate in inpatients and their family members sharing toilet with the first case was significantly higher than in those who sharing no toilet with the case ( χ² =3.907, P<0.05). No risk factors from water and food samples were found. Twenty cases’ samples were positive for norovirus GⅡ and one mop surface smear collected in the ward was positive for norovirus GⅡ.

ConclusionThe outbreak of acute gastroenteritis in the inpatients, which was identified as a nosocomial infection event, was caused by norovirus GⅡ. The infectious source was the inapparent infected person or virus carrier. The spread of the virus was through the human-environment-human mode through the use of some contaminated mops in the ward. So, after targeted measures were taken, the outbreak was controlled effectively.