To identify the source and the risk factors of an acute gastroenteritis outbreak.

Retrospective case analysis was carried out on 111 gastroenteritis patients in a primary school in Nanjing from April 26, 2017 to May 5, 2017. Among them, 64 cases were males and 47 cases were females, who aged from 7 to 36, and the average age was (10.84 ± 4.00). Case-control study were used to investigate suspected transmitted factors by choosing 55 cases among first, third and fifth grade and 55 healthy asymptomatic student controls from same class and sex. TaqMan Real-Time Reverse Transcription–PCR(RT-PCR) was used for testing the specimens from the people, environment and food.

A total of 111 cases were found in this outbreak. Of which, 108 were students (95.7%), 3 cases were teachers (2.6%). Among 11 GII norovirus positive specimens(12.6%), nine were rectal swabs from student cases(56%), one was stool(100%), the other one was doorknob smear of Class One Grade Three(3.33%). The case-control study showed that the distance from patient’vomit in one meter was easy to get infected(OR=3.90, P<0.05), indicated that direct or indirect exposure to vomit or vomit aerosol was risk factor, and we did not find any statistical association between other factors and this outbreak.

The incident of an acute gastroenteritis is caused by Norwalk GII virus infection. Close contact and exposure of patients’ vomit are the major risk factors of the outbreak.