Etiological analysis of two acute gastroenteritis outbreaks caused by norovirus GII.2

Abstract

Objective To determine the cause of two outbreaks of acute gastroenteritis in two kindergartens in Changping district, Beijing in 2016. Methods Stool samples were collected from children with diarrhea and their close contacts. All stool samples were detected with real-time RT-PCR. Some positive specimens were selected to amplify the capsid genes of norovirus by one-step RT-PCR and the PCR products were sequenced directly. Multiple sequence alignments were performed by BioEdit, and phylogenetic tree was constructed by Mega software 6.06. Results Thirty-seven positive strains of GII norovirus were detected in 70 stool specimens, the positive rate was 52.86%, and GI norovirus were not found. Sequences of 13 positive specimens (5 from kindergarten 1, 8 from kindergarten 2) indicated that the virus belonged to norovirus GII.2 genotype. The homology between the strains from Kindergarten 1 and Kindergarten 2 was 99.6%. The nucleic acid sequence homology analysis showed that the strains from Kindergarten 1 and Kindergarten 2 had high homology with norovirus reference strains from Beijing (KY421122) and Jiangsu (KY421121) obtained in 2016. The strains in this study belonged to a big cluster with reference norovirus GII.2 genotype strains, which shared the higher nucleotide identity with other three strains from China (KY457736, KY421122, KY421121). Conclusions The outbreaks of acute gastroenteritis in the two kindergartens were caused by GII.2 noroviruses. The survey and prevention should be strengthened. Key words: Noroviruses; Outbreak; GII.2 genotype; Phylogenetic tree