ObjectiveTo study the epidemiological characteristics and identify the cause of an outbreak caused by norovirus infection in a school in Hebei province in 2018, and evaluate the performance of the epidemic response.
MethodsField epidemiology method were used to collect basic information of an outbreak in a school in Hebei province in 2018 and retrospective questionnaire survey was conducted for all cases, followed by descriptive analysis of the outbreak. Risk factors related to the outbreak were explored through cross-sectional and case-control study. Meanwhile, laboratory tests of enteroviruses and bacterial pathogens were performed by using stool samples and anal swabs of the patients, food and water samples, and environment samples.
ResultsThe outbreak lasted for 6 days, involving 55 cases. The cases mainly occurred in 16 classes, and the attack rate was 1.60%. Among the cases, 34 were males, and 21 were females, with the ratio of 1.62∶1. The age of the cases ranged from 6 years to 37 years, with the average age of 9.13 years. The main clinical symptoms were vomiting (92.73%, 51/55), diarrhea (65.45%, 36/55), which all disappeared within 1 or 2 days after onset. No death and server case occurred. Risk factor analysis showed that the differences in food intake and water drinking were not significant between class with high attack rate and class without case. A total of 19 samples of the cases were collected, in which 11 were positive for norovirus GⅡand 1 was positive for astrovirus. In addition, in 41 samples of food and water, no enterovirus was detected and the bacterial indexes were also within normal range.
ConclusionThe outbreak was caused by norovirus GⅡ. Vomit aerosol transmission and person to person contact were main transmission routes in this outbreak. Untimely discovery and isolation of the first case, improper dispose of vomit and disinfection were the facilitating factors for the disease spread and outbreak.
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