Epidemiological Characteristics Of Norovirus In Lanzhou From 2015 To 2018 And In Part Of China In 2018

PART 1 EPIDEMIOLOGICAL CHARACTERISTICS OF NOROVIRUS IN LANZHOU FROM 2015 TO 2018Objective:To understand the molecular epidemiological characteristics of children with Norovirus-associated gastroenteritis under 5 years old in Lanzhou from2015 to 2018.Method:The fecal specimens and related clinical information of children with Norovirus-associated gastroenteritis under 5 years old in Lanzhou from January 2015to December 2018 were collected.Amplification and sequence analysis were performed with RT-PCR.Statistical methods were used to analyze the epidemiological characteristics of Norovirus during the four years.Results:The detection rate of Norovirus was 14.27%(112/785).The detection rate of Norovirus from 2015 to 2018 was 7.89%-17.98%.Compared with the positive rate in different years,the difference was statistically significant(?~2=9.760,P=0.021);seasonal peaks occurred in September 2015(35.71%),May 2016(41.67%),January2017(35.29%)and October 2018(26.92%).There was no statistically significant difference in the distribution of norovirus infection among children in urban and rural areas and rural areas(?~2=3.301,P=0.069).There was no statistically significant difference in fever rate,diarrhea rate and vomiting rate between different genders(?~2=0.057,P=0.812,?~2=0.016,P=0.900,?~2=0.783,P=0.376).There was no statistical difference in fever rate among children with diarrhea in different age groups(?~2=0.462,P=0.927).There was no statistically significant difference in diarrhea rate among children with norovirus gastroenteritis in different age groups(?~2=0.383,P=0.984).There was no significant difference in vomiting rate among children in different age groups(?~2=3.201,P=0.525).The detection rate was highest at 1 to 2years old(16.8%)and lowest at 2 to 3 years old(10.0%),with no statistical difference.According to genotyping results,GII.4 Sydney 2012[P31]and GII.3[P12]were the main predominant strains with detection rates of 54.5%(61/112)and 36.6%(41/112),respectively.Other genotypes include GI.6[P6](1),GII.2[P16](1),GII.17[P17](1),GII.6[P7](6)and GII.4_Neworleans 2009[P4](1).Conclusion:Norovirus in children with acute gastroenteritis in Lanzhou is mainly in GII group,and its genotype is diverse.And GII.4 Sydney 2012[P31]and GII.3[.P12]are the main epidemic strains.PART 2 EPIDEMIOLOGICAL CHARACTERISTICS OF NOROVIRUS IN PART OF CHINA IN 2018Objective: To understand the molecular epidemiological characteristics of children with Norovirus-associated gastroenteritis under 5 years of age,to identify the dominant genotypes of norovirus in parts of China in 2018,and to provide a scientific basis for the molecular evolution mechanism of norovirus and its vaccine research in China.Method: Fecal samples and corresponding clinical data about children under 5 years old with Norovirus-associated gastroenteritis are Collected from January 2018 to December 2018 in parts of China(including Haerbin,Jilin,Henan,Sichuan,Shenyang,Shenzhen,Neimenggu,Anhui).Amplification and sequence analysis were performed with RT-PCR.The statistical characteristics of norovirus molecular epidemics in parts of China in 2018 were analyzed using statistical methods.Results: A total of 412 samples of norovirus infection were detected in children with Norovirus-associated gastroenteritis under 5 years old in eight provinces;there were 161 children from 6-month to 24-month(including 6-month)group,accounting for 39.08%(161/412)of the virus infected population;Norovirus-positive specimens had the largest number of cases detected in the fall(123 cases),accounting for 29.85% of the total number of cases tested,followed by winter(113 cases).There was a statistically significant difference in fever rate among children with diarrhea in different age groups ?2=11.022,P=0.051);The difference in vomiting rate among children of different genders was no statistically significant(?2=1.178,P=0.278);There was a statistically significant difference in the vomiting rate among children with diarrhea in different age groups(?2=34.771,P=0.000).A total of 13 genotype combinations were found in the study: GI.6 [Pb](1);GI.3 [Pd](4);GII.4 Sydney [P31](164);GII.3 [P12](116);GII.2 [P16](18);GII.3 [P16](1);GII.4 [P16](1);GII.4 Sydney [P16](4);GII.17 [P17](4);GII.13 [P21](2);GII.3 [P4](2);GII.4 Sydney [P4](2);GII.6 [P7](7).GII.4 Sydney [P31] is an epidemic strain in June,October,and December.GII.3 [P12] is more common in May,October,November,and December,and GI genotype is more common in January to June;the remaining genotypes are distributed in different months.The number of GII.P12 genotype mutations in the polymerase region was the largest,and the number of GII.P31 genotype mutations was the second.The GII.4 genotype of the capsid region found the largest number of nucleotide mutation sites,and the GII.3 genotype found a total of 10 nucleotide mutation sites.This result may explain why GII.4 Sydney [P31] and GII.3 [P12] are the main epidemic gene combinations.Conclusion: Norovirus infection in children with acute gastroenteritis under 5 years of age in part of China in 2018 took GII.4 Sydney [P31] and GII.3 [P12] as the main epidemic gene combinations,and its genotype is diverse.The rate of norovirus infection in children under 5 years of age increased significantly from October to December,and the infection occurred throughout the year,showing a small fluctuation in peaks.