An epidemic of mixed infection of norovirus GⅠ and GⅡ

ObjectiveTo investigate an epidemic of norovirus infection, identify the pathogen and transmission factors, and provide evidence for the response of similar epidemic.

MethodsThe cases were searched, and case survey and field hygiene survey conducted. The risk factors were analyzed through case-control study. The stool samples were collected from the cases for norovirus nucleic acid detection with real time fluorescence reverse transcriptase polymerase chain reaction.

ResultsA total of 16 confirmed cases were found, the attack rate was 5.82% (16/275). The cases were all students, no teacher and school staff were affected. No severe case and death occurred. Acute illness was observed in the cases, the clinical manifestations included vomiting (100.0%), nausea (100.0%), abdominal pain (62.5%) and fever (25.0%); Thirteen norovirus positive samples were detected in 16 stool samples, i.e. 2 norovirus GⅠ and GⅡ mixed positive samples, 2 norovirus GⅠ positive samples, 9 norovirus GⅡ positive samples. Off-campus boarding (OR＝154, 95% CI: 19.82–1 196.45) and onlooking at vomiting sites were risk factors for the infection (OR＝143, 95% CI: 18.31–1 116.71).

ConclusionThe epidemic was a norovirus caused infection cluster, which might be caused by aerosol transmission through the inhalation of vomit of the index case.