Genetic Diversity and Epidemiology of Norovirus in Children with acute sporadic gastroenteritis in Shanghai, China, 2012-2017

Abstract

Background Noroviruses are considered the important causes of acute gastroenteritis (AGE) across all age groups especially in children under five years. We investigated the prevalence and molecular epidemiology of norovirus in outpatient children from Children’s Hospital of Fudan University in Shanghai, China. Methods A total of 1433 stool specimens were collected from children under five years with acute gastroenteritis between January 2012 and December 2017. All the samples were analyzed by conventional reverse transcription-polymerase chain reaction (RT-PCR) for genogroup II targeting both the RNA-dependent RNA polymerase (RdRp) and partial capsid genes. Norovirus Genotyping Tool v.2.0 (https://www.rivm.nl/mpf/typingtool/norovirus/) was used for genotyping strains, and phylogenetic analyses were conducted by MEGA 6.0. Results During 2012 to 2017, NoVs were detected in 15.4% (220/1433) of the samples, with high detection rate in children aged 7-12 months (19.2%, 143/746) and in September (27.7%, 33/119). Based on genetic analysis of RdRp, GII.Pe (74.5%%, 137/184) was the most predominating RdRp genotype from 2013 to 2017 while GII.P4 played a dominant role in 2012 (55.6%, 21/36). The most prevalent NoVs genotype was GII.4 (73.6%, 162/220) during 2012 to 2017 among the capsid genotypes. According to genetic analysis of RdRp and capsid sequences, the strains were clustered into 19 RdRp/capsid genotypes, and 12 of them were discordant RdRp and capsid genotypes, such as GII.Pe/GII.4-Sydney_2012, GII.P12/GII.3, GII.P7/GII.6, GII.Pe/GII.3, GII.P16/GII.2. GII.Pe/GII.4-Sydney_2012 was completely instead of the pandemic of GII.P4-2006b/GII.4-2006b since 2013 and distributed across all age groups in children. Conclusions The present study shows high detection rates and genetic diversity of circulating NoVs genotypes in paediatric AGE samples from Shanghai. The findings emphasize the importance of continuous molecular surveillance of emerging NoVs strains.