An acute gastroenteritis outbreak caused by human astrovirus in Bao'an district of Shenzhen, 2017

ObjectiveTo explore the pathogens and transmission risk factors of an acute gastroenteritis outbreak occurred in a school in Bao'an district, Shenzhen in 2017.

MethodsAccording to the case definition, cases were searched in the school from October to November 2017. Descriptive epidemiological method was used for data analysis. Five classes with high attack rates were selected as the target. A retrospective cohort study was conducted to investigate the possible risk factors in 269 students, including their exposure history, dining and drinking habits. The survey data were used for logistic regression analysis. Stool samples and anal swabs of some infected cases, water samples from drinking fountains, barrelled water samples, and toilet water samples were collected for the detections of rotavirus, astrovirus, adenovirus, norovirus, and sappovirus by fluorescence PCR.

ResultsA total of 98 cases were identified in the school from October 20 to November 17, 2017. The overall attack rate was 3.21% (98/3 052). The attack rate was 3.59% in boy students (61/1 698) and 2.73% in girl students (37/1 354), respectively. No significant difference was found between boys and girls (χ²＝1.782, P＝0.181). The highest attack rate (3.94%, 6/152) was reported in students in teaching building 3, followed by 3.62% (84/2 319) in students in main teaching building. Significant differences in attack rate were found in attack rates among the students in different teaching buildings (χ²＝7.837, P＝0.049). There was no significant differences in attack rate among students in classes on different floors of the main teaching building(χ²＝1.861, P＝0.713). In this study, 269 students were investigated. Results of the retrospective cohort study showed that direct drinking water (RR＝6.975, 95% CI: 1.871–26.027) and case contact (RR＝6.514, 95% CI: 2.314–18.358) were the risk factors of this outbreak. The overall human astrovirus positive rate of the stool samples and anal swabs was 28.00% (7/25). No human astrovirus was detected in water samples.

ConclusionThis outbreak of human astrovirus infection was mainly caused through contact transmission. It is recommended that schools conduct early detection, isolation, and reporting of communicable disease cases to minimize the exposure in healthy students.