2020年北京地区儿童中急性胃肠炎相关诺如病毒的分子流行病学特征

Molecular epidemiology of norovirus associated with pediatric acute gastroenteritis in Beijing in 2020

目的探讨北京地区2020年疫情防控措施下急性胃肠炎患儿诺如病毒的分子流行病学特点。方法采用回顾性重复横断面研究方法,2020年收集首都儿科研究所附属儿童医院就诊急性胃肠炎患儿的粪便标本或呕吐物标本1213份。首先用实时荧光反转录PCR进行标本中诺如病毒筛查,然后用反转录PCR对诺如病毒阳性标本进行病毒VP1基因和RdRp基因扩增,据核苷酸序列进行基因分型。采用χ^(2)检验对不同标本类型、患儿不同性别及不同年龄组间诺如病毒的检出阳性率进行比较。结果在1213份急性胃肠炎患儿标本中,共筛查到诺如病毒阳性标本215份,全年的检出阳性率为17.7%,阳性病例集中在秋冬季节[1、10、11及12月阳性率分别为28.6%(18/63)、26.2%(16/61)、22.8%(77/338)以及17.1%(89/520)]。粪便标本的阳性率明显高于呕吐物标本(χ^(2)=9.692,P<0.01),而男女性别差异无统计学意义(χ^(2)=0.041,P>0.05),各年龄组间诺如病毒检出率差异有统计学意义(χ^(2)=103.112,P<0.01),以6~48月龄诺如病毒的检出率较高。对G基因型分析显示共有3个基因群(GⅠ、GⅡ和GⅨ)诺如病毒流行,以GⅡ基因群为主,占总数的98.5%(196/199)。而GⅡ基因群中以GⅡ.4 Sydney为主要流行株,占GⅡ基因群的55.1%(108/196);其次为GⅡ.2型(29.6%,58/196),以往流行的GⅡ.3型(10.2%,20/196)诺如病毒在本次监测周期中较少。诺如病毒P基因型分析结果显示以GⅡ.P16为主,占61.5%(96/156);其次为GⅡ.P31(19.9%,31/156)。双基因测定结果显示以GⅡ.4 Sydney[P16]为主,占36.4%(56/154),其次为GⅡ.2[P16]占24.7%(38/154)。结论2020年诺如病毒的总阳性率与以往没有大的区别,但流行的基因型别构成有了明显的改变,且呈现多种基因型别诺如病毒的同时流行。

Objective To investigate the molecular epidemiology of norovirus associated with pediatric acute gastroenteritis in Beijing under the Working Mechanism for Joint Prevention and Control of the Epidemic in 2020.Methods This was a retrospective,repeated cross-sectional study.Fecal or vomit samples(1213 cases)were collected from children visited the Capital Institute of Pediatrics Affiliated Children′s Hospital for acute gastroenteritis from January 1 to December 31,2020.First,real-time reverse PCR(RT-PCR)was used to screen the samples for norovirus,and then RdRp gene and capsid gene VP1 of norovirus-positive samples were amplified by conventional RT-PCR for genotyping based on the nucleotide sequence.The χ^(2) test was used to compare the positive rates and genotypes of norovirus among different specimen types,genders of children,and different age groups.Results Among the 1213 samples were collected,215 samples were positive for norovirus,with a positivity rate of 17.7%for the whole year.The peak of norovirus infection observed mainly in the cold seasons,as the positive rates were 28.6%(18/63),26.2%(16/61),22.8%(77/338)and 17.1%(89/520)in January,October,November and December,respectively.The positive rate of norovirus in fecal sample was significantly higher than that in vomit sample(χ^(2)=9.692,P<0.01).There was no significant difference between genders(χ^(2)=0.041,P>0.05),but significant difference was found between age groups with the highest rate in the 6-48 months group(χ^(2)=103.112,P<0.01).Three genogroups(GⅠ,GⅡand GⅨ)of the circulating virus were detected by G-gene typing,and GⅡgenogroup was predominant,accounting for 98.5%(196/199).Among the GⅡpositive samples,genotype GⅡ.4 Sydney(55.1%,108/196)was the most common,followed by GⅡ.2(29.6%,58/196),while the GⅡ.3 norovirus(10.2%,20/196)which was common in previous years was not as much as before.Based on the P-type,GⅡ.P16 was predominant(61.5%,96/156),followed by GII.P31(19.9%,31/156).The dual genotyping revealed that GⅡ.4 Sydney[P16](36.4%,56/154)and GⅡ.2[P16](24.7%,38/154)were predominant.Conclusion The prevalence of norovirus in children in 2020 in Beijing is not much different from those of the previous years,but the genotypes composition has changed significantly,and there are multiple genotypes circulating simultaneously.