一起诺如病毒感染性腹泻暴发疫情流行病学调查

目的了解一起诺如病毒感染性腹泻暴发的特点和流行原因，探讨暴发疫情调查处理的经验，为制定防治对策提供科学依据。方法对开平市月山镇一起诺如病毒暴发疫情用流行病学方法进行分析。结果该镇水井片11月25日至12月5日共发生感染性腹泻238例，罹患率4．18％；患者各年龄组均有发病，青壮年居多；患者大多呈腹泻、呕吐等胃肠炎症状，病情较轻；对搜索到的575户2347人进行发病聚集性分析，发现有明显的家庭聚集性；不同村委会发病差异有统计学意义。部分病人粪便标本经检测诺如病毒阳性。疫情经加强饮用水消毒、病人隔离治疗、开展爱国卫生运动和健康教育等综合措施后得到控制。结论本起暴发疫情由诺如病毒感染引起，供水系统受到一过性污染是引起水源性暴发的主要原因。加强饮用水的消毒与管理，开展健康教育是控制疫情的关键。     

一起诺如病毒Ⅰ型Ⅱ型混合感染急性胃肠炎暴发疫情调查分析

目的 对湖州市某中学发生的一起以腹泻、呕吐为特征的暴发疫情进行调查和分析,查找病因、分析危险因素.方法 采用现场流行病学调查方法,结合临床表现及实验室检测结果进行调查与综合分析.结果该校共发生急性胃肠炎病例578例,罹患率为23.58%;临床表现主要为腹泻、呕吐、腹痛、恶心,少见发热,大多症状较轻,病程1～3 d;各班均有发病,无明显聚集性;共采集患者粪便标本15份,采用RT-PCR方法检出诺如病毒阳性标本11份,其中Ⅱ型6份,Ⅰ型阳性3份,Ⅰ型、Ⅱ型混合阳性2份(同一学生,两次采样).病例对照研究显示,饮用未加热桶装水是此次发病的危险因素(OR=2.46,95% CI=1.19～5.23),且饮水量与发病存在剂量反应关系(X2=24.18,P<0.01).通过采取隔离治疗传染源、改桶装水为供应开水、卫生消杀及健康教育等综合措施后,疫情迅速得到控制.结论 本次疫情是由诺如病毒引起的急性胃肠炎暴发,可疑的传播途径为饮用未加热的桶装水与日常接触.     

感染性腹泻疫情中诺如病毒的分子流行病学分析

目的 研究感染性腹泻疫情中诺如病毒的分子流行病学特点.方法 对2008-2010年湖州地区的感染性腹泻疫情标本共119份进行诺如病毒核酸检测,并选取部分阳性扩增产物经序列测定分析诺如病毒的基因型.结果 119份感染性腹泻标本荧光定量PCR检测阳性50份,其中GⅠ型9份,GⅡ型35份,GⅠ和GⅡ混合感染6份.对12份PCR扩增阳性产物进行序列分析显示：5株GⅠ型诺如病毒毒株分属于GⅠ/2和GⅠ/3两种基因型;7株GⅡ型诺如病毒毒株中除1株属于新基因型GⅡb外,其余6株均属于GⅡ/4基因型.结论 诺如病毒是引起湖州地区感染性腹泻疫情最重要的病原菌之一,且湖州地区的诺如病毒存在很高的遗传多样性,同时也存在基因型别的差异.     

Molecular epidemiology of norovirus variants detected in children under five years of age in Hyderabad,India

PurposeNoroviruses are common viral agents in acute diarrhea in all age groups worldwide. Norovirus has been classified into 10 genogroups, GI to GX with over 48 genotypes among them the GII.4 genotype has evolved over time with a clear pattern of periodic variant replacement. Immunity is strain or genotype specific with little or no protection conferred across genogroups. The present study was aimed to determine the epidemiology, prevalent genotypes of norovirus in children below five years of age in the Hyderabad region, India.MethodsThe stool samples and clinical data were collected from 458 children below 5 years of age comprising of cases with acute gastroenteritis (n ?= ?366) and a control group (n ?= ?92) admitted to the pediatric ward. All the samples were tested for Norovirus by ELISA and RT-PCR. Sequencing was done for predominant strains.Results10.3% (n ?= ?38) of cases and 3.2% (n ?= ?3) of the control group were found to be Norovirus positive. Predominant genotypes were GII-82.5% followed by GI-12.5%.ConclusionSequencing and Phylogenetic analyses of 20 GII.4 strains was done. All of the isolates are clustered away from published the GII.4 variants thus suggesting the appearance of a new variant.     

Molecular characterization of three novel murine noroviruses

Murine noroviruses (MNV) comprise a group of newly recognized pathogens infecting laboratory mice. The first reported murine norovirus, murine norovirus 1 (MNV-1), produces a transient infection with a short duration of fecal shedding after infection of immunocompetent laboratory mice. Our laboratory subsequently isolated three novel murine noroviruses, murine norovirus 2 (MNV-2), murine norovirus 3 (MNV-3), and murine norovirus 4 (MNV-4), that have markedly different pathogenicity from MNV-1 by producing persistent infections and prolonged fecal shedding in infected immunocompetent mice. In this study, the nucleotide sequences and the predicted amino acid sequences of the three novel murine noroviruses were determined and compared to each other, MNV-1, and other previously described human and animal noroviruses. The three novel murine norovirus strains were shown to be related to each other and MNV-1 by sequence and phylogenetic analysis even though MNV-2, MNV-3 and MNV-4 all display markedly different biologic behavior from that of MNV-1. The nucleotide sequence data reported in this paper have been submitted to the GenBank nucleotide sequence database and have been assigned the accession numbers DQ223041, DQ223042, and DQ223043.     

诺如病毒衣壳蛋白重组人3型腺病毒的构建

目的 制备表达诺如病毒衣壳蛋白的重组人3型腺病毒.方法 将诺如病毒衣壳蛋白基因(Noro-orf2)克隆到腺病毒穿梭载体pBSE3CMV-egfp上,与线性化人3型腺病毒骨架质粒pBRAdv3共电转化感受态大肠杆菌BJ5183,使其在细菌内发生同源重组,带Noro-orf2基因的表达框置换腺病毒E3区,PCR及酶切筛选得到重组腺病毒质粒,将重组腺病毒质粒转染Hep-2细胞进行包装,获得感染性的重组腺病毒粒子,免疫组化分析重组腺病毒中诺如病毒衣壳蛋白的表达.结果 同源重组后经酶切和PCR鉴定证明插入Noro-orf2基因的重组腺病毒质粒pBRAdv3E3dNor成功构建,并经转染包装得到高滴度的重组腺病毒Adv3E3dNor,免疫组化证明诺如病毒衣壳蛋白得到表达.结论 成功构建表达诺如病毒衣壳蛋白的重组3型腺病毒Adv3E3dNor,为研制人3型腺病毒-诺如病毒双价疫苗奠定了基础.     

Cost-effectiveness of pediatric norovirus vaccination in daycare settings

ObjectiveNoroviruses are the leading cause of acute gastroenteritis in the United States and outbreaks frequently occur in daycare settings. Results of norovirus vaccine trials have been promising, however there are open questions as to whether vaccination of daycare children would be cost-effective. We investigated the incremental cost-effectiveness of a hypothetical norovirus vaccination for children in daycare settings compared to no vaccination.MethodsWe conducted a model-based cost-effectiveness analysis using a disease transmission model of children attending daycare. Vaccination with a 90% coverage rate in addition to the observed standard of care (exclusion of symptomatic children from daycare) was compared to the observed standard of care. The main outcomes measures were infections and deaths averted, quality-adjusted life years (QALYs), costs, and incremental cost-effectiveness ratio (ICER). Cost-effectiveness was analyzed from a societal perspective, including medical costs to children as well as productivity losses of parents, over a two-year time horizon. Data sources included outbreak surveillance data and published literature.ResultsA 50% efficacious norovirus vaccine averts 571.83 norovirus cases and 0.003 norovirus-related deaths per 10,000 children compared to the observed standard of care. A $200 norovirus vaccine that is 50% efficacious has a net cost increase of $178.10 per child and 0.025 more QALYs, resulting in an ICER of $7,028/QALY. Based on the probabilistic sensitivity analysis, we estimated that a $200 vaccination with 50% efficacy was 94.0% likely to be cost-effective at a willingness-to-pay of $100,000/QALY threshold and 95.3% likely at a $150,000/QALY threshold.ConclusionDue to the large disease burden associated with norovirus, it is likely that vaccinating children in daycares could be cost-effective, even with modest vaccine efficacy and a high per-child cost of vaccination. Norovirus vaccination of children in daycare has a cost-effectiveness ratio similar to other commonly recommended childhood vaccines.     

Terminal modifications of norovirus P domain resulted in a new type of subviral particles, the small P particles

The protruding (P) domain of norovirus VP1 is responsible for immune recognition and host receptor interaction. Our previous studies have demonstrated that a modification of the ends of the P domain affects the conformation and/or function of the P protein. An expression of the P domain with or without the hinge, or with an additional cysteine at either ends of the P protein resulted in P dimers and/or P particles. Here we report a new type of subviral particle, the small P particles, through a further modification, either an addition of the flag tag or a change of the arginine cluster, at the C-terminus of the cysteine-containing P domain. Gel filtration and cryo-EM studies showed that the small P particles are tetrahedrons formed by 6 P dimers or 12 P monomers that is half-size of the P particles. Fitting of the crystal structure of the P domain into the cryo-EM density map of the particle indicated similar conformations of the P dimers as those in P particles. The small P particles bind human HBGAs and are antigenically reactive similar to their parental VLPs and P particles. These data suggest that the C-terminus of the P domain is an important factor in the formation of the P particles. Further elucidation of the mechanism of these modifications in the P particle formation would be important in structure biology and morphogenesis of noroviruses. The small P particles may also be a useful alternative in study of norovirus-host interaction and vaccine development for noroviruses.     

2016-2018年广州儿童腹泻诺如病毒检测及流行状况分析

目的了解2016-2018年广州地区儿童腹泻中诺如病毒感染的情况,为临床诊断和病毒性腹泻疾病的防控提供可靠数据。方法收集2016年1月至2018年12月住院和门诊的腹泻12岁以下儿童粪便标本856份,采用荧光定量RT-PCR检测方法检测诺如病毒核酸,确定是否感染阳性,并从患者感染年龄、性别、时间等方面比较分析。结果856例腹泻标本中,诺如病毒感染阳性259例,阳性率为30.25%;其中不同年龄段腹泻儿童的诺如病毒检出阳性率依次分别为0~1岁组35.11%(构成比53.28%),1~2岁组30.13%(构成比16.99%),2~3岁组32.47%(构成比19.31%);0~3岁儿童阳性率构成比共占89.58%;以每年11~12月(冬季)和1~3月(春季)为发病高峰期(5个月构成比为81.47%);从病毒不同基因型分析,GI型和GII型诺如病毒检出率分别为10.9%和19.4%。结论诺如病毒是导致儿童腹泻的重要病原之一,0~3岁儿童是诺如病毒的易感人群,以冬春季节为流行高峰,GII型为主要基因型。