ObjectivesTo explore the possible transmission route and risk factors for an outbreak of norovirus infectious diarrhea in a kindergarten in Guangzhou, and provide evidence for the development of epidemic prevention and control measures.

MethodsOn 24 October, 2019, the case definition was developed and field epidemiological investigation was carried out. Relevant information were collected by using self-made questionnaire for a case control study and anal swabs were taken from cases and related persons for fluorescent quantitative PCR detection.

ResultsA total of 25 cases of infectious diarrhea were reported in this outbreak from 13 to 24 October, 2019, with an attack rate of 9.80% (25/255). No severe cases or deaths were reported; The main clinical manifestations of the case were vomiting (96.00%); The epidemic curve suggested a human to human transmission pattern after point source exposure; Cases mainly occurred in a class on the second floor of the teaching building, and the differences in incidence rates among different floors and classes were significant (P＜0.05); All the cases were young children. Among these cases, 11 were boys with an attack rate 9.56% and 14 were girls with an attack rate of 10.20%, the difference was not significant (χ²＝0.343, P＝0.558); Exposure to patients within 3 days before onset (OR＝8.308, 95% CI: 1.831–37.698), exposure to patients' vomit within 1 meter (OR＝6.429, 95% CI : 1.368–30.209) and playing large toys in the kindergarten in epidemic period (OR＝57.255, 95% CI : 8.390–390.718) were risk factors for the infection. No nucleic acid of norovirus GⅡ.4 was detected in 24 anal swabs.

ConclusionIt is an outbreak of infectious diarrhea caused by norovirus GⅡ.4. Human to human spread was the transmission route of this outbreak. In order to prevent and control the incidence of norovirus gastroenteritis and other diseases in kindergarten, it is suggested to strengthen the training of teaching staff on knowledge of infectious disease prevention, strengthen ventilation and sanitation and disinfection, and conduct morning and afternoon check-up and absenteeism registration due to illness in kindergartens to protect the health of children.