| Norovirus(Novs)has become the main pathogen causing the global acute viral diarrhea(AGE)outbreak.Every year,the global economic burden caused by infection with the virus is approximately $6 billion,with over 2.19 million people hospitalized and 20.02 million deaths.Norovirus,referred to as Novs for short,is a non enveloped single stranded positive RNA virus of the genus Konoru,calicivirus,with a total length of about 7500 bp.In 2013,the Novas Classification Working Group(NCWG)officially established the naming rules for this virus,which is named jointly by the VP1 gene and the Rd Rp gene.As of 2019,Novas has a total of 12 genomes(GI-GX,GNA1,and GNA2)and 49 genotypes.In the United States,Europe,and Japan,up to 93% of non bacterial gastroenteritis outbreaks and 60-85% of gastroenteritis outbreaks are associated with Novs.In Africa,the overall prevalence of norovirus is very high,and genotype II and GII.4 are dominant.In recent years,GII.4 [P16],GII.2 [P16],and GII.12 [P16] have become newly emerging epidemic genotypes worldwide.GII.4 is still the main type of transmission worldwide,and new mutants are generated every 2-3years,followed by GII.3,followed by GII.2,GII.17,GII.6,GI.3,GII.13,GI.4,GII.12,and GII.14.In China,different genotypes of Novs have caused multiple outbreaks in different provinces and cities,including Guangdong,Zhejiang,Jiangsu,Sichuan,Beijing,and Shanghai.Among them,GII.4,GII.17,and GII.2 have caused widespread transmission in China,with rapid transmission speed and wide spread area.In addition,Novs has a significant seasonality in China,with the vast majority of Novs diseases peaking from October to March of the next year.Although China has established a monitoring system for Novs,the detection areas are mostly concentrated in the coastal areas,and there is still a lack of monitoring for the southwest region.Due to the special geographical location and climate of Kunming City,as well as the strong infectivity,wide range of transmission,and rapid mutation rate of the virus,it is necessary to understand the prevalence and transmission of Novs in this province.This study took the onset of acute viral gastroenteritis in children from 2012 to 2022 as a starting point,and conducted a Novs sampling test on them using RT-PCR.By establishing a phylogenetic tree,we can understand the prevalence and transmission of different genotypes of the virus in the child population,as well as the relationship between clinical symptoms and genotypes.After analysis,The results are shown as follows :Firstly,in order to study the epidemiological changes of Novs,we randomly selected 249 samples from Kunming City from 2021-2022.RT-PCR was used to amplify and sequence the VP1 gene and Rd Rp gene of the virus,and 249 samples were successfully amplified.The results showed that there were GII.4[P16](47.77%)、GII.4[P31](18.22%)、GII.6[P7](18.22%)、GII.3[P12](4.86%)、GII.3[P25](2.83%)、GII.17[P17](2.83%)、GII.2[P16](0.40%)、GII.4[P12](0.40%)、GII.7[P7](2.43%)、GII.15[P15](0.81%)、GII.13[P17](0.40%)、GII.13[P16](0.40%)、and GII.13[P21](0.40%),a total of 13 genotypes,Two samples that were not accurately typed appeared.Presents a popular feature dominated by GII.4 [P16],GII.4 [P31],and GII.6 [P7].In addition,we conducted statistical studies on VP1 gene and Rd Rp genotyping.For the VP1 gene,there are GII.4(65.99%)、GII.6(18.22%)、GII.3(7.69%)、GII.17(2.83%)、GII.7(2.43%)、GII.13(1.21%)and GII.15(1.21%),presenting the main epidemic characteristics of GII.4,GII.6,and GII.3.For the Rd Rp gene,there were P16(48.58%),P7(20.65%),P31(17.81%),P12(5.26%),P17(3.24%),P25(2.83%),P15(1.21%)and P21(0.40%),presenting the main epidemiological characteristics of P16,P7,and P31.Secondly,children infected with Novs virus caused clinical symptoms such as diarrhea,vomiting,high fever,neck stiffness,convulsions,photophobia,and delayed response.In order to understand the relationship between the virus genotype and the clinical symptoms,we collected 61 patients with clinically severe symptoms(high fever n=13,neck stiffness n=12,convulsion n=57,photophobia n=1,and delayed response n=16)and conducted a typing study on them.The results showed that convulsions(31.5%),vomiting(23.3%),diarrhea(21.9%),fever above 38 ℃(7.5%),and neck stiffness(6.8%)were observed in GII.4 [P16];The GII.4 [P31] genotype showed seizures(33.3%),diarrhea(28.6%),vomiting(9.5%),neck stiffness(9.5%),and delayed response(9.5%);In GII.6 [P7],convulsions(42.9%),vomiting(28.6%),delayed reactions(14.3%),and fever greater than 38℃(14.3%)were observed;In GII.3[P12],diarrhea,vomiting,and convulsions each accounted for 33.3%.Finally,we conducted full-length amplification and recombination analysis on two samples that could not be accurately typed,and found that sample 899 had undergone recombination at ORF2 and ORF3,with a genomic nucleotide difference of 13.8% to16.8%.The VP1 genotype was GII.4 Sydney,and the Rd Rp genotype was P7,producing a suspected new recombinant.In summary,this study found that Novs virus is widely spread in Yunnan Province,causing various clinical symptoms such as diarrhea,vomiting,and high fever in children.The genotype of the epidemic virus strain has also changed,and new recombinant subtypes have been found.Therefore,this study conducted an in-depth analysis of the genotype and clinical symptoms of Novs virus in Kunming City for the first time,providing theoretical support for understanding the prevalence of viral gastroenteritis in children caused by Novs virus in Yunnan Province,and providing direction for clinical diagnosis. |
