Genetic diversity of norovirus associated with outbreaks in school children with acute gastroenteritis in Changzhou, China, 2018-2019

Norovirus is one of the major causes of outbreaks and sporadic cases of acute gastroenteritis in school children. Obtaining local genotype diversity information regarding norovirus is important for developing and evaluating prevention strategies of the transmission of this virus in school children. Clinical specimens, obtained from the routine acute gastroenteritis surveillance network from 2018 to 2019, were primarily tested using commercial real-time PCR Kit. Samples with Ct value less than 25 were selected and used for complete genome sequencing and those with Ct value between 25 and 30 were selected and used for he partial VP1 and RdRp regions sequencing. Phylogenetic trees of the viral genome were constructed by using the neighbor-joining method with bootstrap analysis of 1000 replicates in MEGA 6.0. Epidemiological surveillance of acute intestinal infections (n = 384) showed high-level detection (73.18%) of human norovirus in school endemic acute gastroenteritis events in Changzhou, with obvious epidemic characteristics in autumn and winter. Through genotyping, it was found that 93.12% of norovirus were GII, including GII.2, GII.3, GII.4, GII.6, GII.7, and GII.17. By October 2019, two norovirus genotypes, GII.4[P31] and GII.17[P17], became the preponderant epidemic strains. Phylogenetic analysis of the new GII.17[P17] complete genomes showed close relationship with Miyagi strain identified in Japan in 2015, and GII.4[P31] showed close relationship with Jinan strain indentified in China in 2017. The study highlights the emerging role of GII.4[P31] and GII.17[P17] in causing endemic acute gastroenteritis outbreaks at school children, in Changzhou, China in 2019.