Identification and tracing of norovirus GⅠ in epidemics of acute gastroenteritis in 6 schools in Xicheng district, Beijing, 2018−2019

  Objective  To analyze the genotype characteristics of norovirus GⅠ detected from the acute gastroenteritis epidemics in 6 schools in Xicheng district of Beijing from 2018 to 2019.

  Methods  A total of 37 stool samples were collected from the acute gastroenteritis cases in the 6 schools during this period. Real-time fluorescent RT-PCR were used to detect the viral nucleic acids of norovirus GⅠ/GⅡ from the samples. The regions coding for RNA polymerase and capsid proteins VP1 of norovirus G I were amplified and sequenced in by RT-PCR. The successfully sequenced virus strains were preliminary identified and genotyped by using on-line Norovirus Typing Tool (Version 2.0). Software BioEdit7.0.9.0 was used for sequence alignment, and software MEGA 6.0 was used to construct phylogenetic tree.

  Results  The acute gastroenteritis epidemics in 6 schools (18 S1−S4 and 19 S5−S6) were caused by norovirus. The positive rate of norovirus GⅠ nucleic acid was 83.78% (31/37), and no norovirus GⅡ was detected. The phylogenetic analysis on polymerase and capsid proteins VP1 region showed that 4 strains from 1 epidemic and GⅠ.Pd and GⅠ. 3b reference strains were in the same branch, and 19 strains from 5 epidemics and GⅠ.Pb and GⅠ.6a reference strains were in the same branch, the similarity of each school strain was 100.0%. The results of bipartition type showed that 1 epidemic was caused by the recombinant strain of GⅠ.Pd-GⅠ.3b, The similarity between GⅠ.Pd-GⅠ.3b and GⅠ. 3P13/Hu/MT008455/2018/Shanghai/chi was 99.6%, and 5 epidemics were caused by the recombinant strain of GⅠ.Pb-GⅠ.6a, the similarity between GⅠ.Pb-GⅠ.6a and GⅠ. 6P11/Hu/MZ227264/2016/US was 98.1%.

  Conclusion  The epidemics of norovirus-induced acute gastroenteritis occurred in 6 schools in Xicheng district of Beijing from 2018 to 2019 were caused by GⅠ.Pd-GⅠ.3b and GⅠ.Pb-GⅠ.6a recombinant strain. It is necessary to strengthen the molecular epidemiological surveillance for norovirus recombinant strains to provide evidence for the early warning and prediction of norovirus infection epidemics.