人感染H7N9禽流感26例临床特征与病毒基因分析研究

目的探讨人感染H7N9禽流感病毒患者的流行病学和临床特征,以及病毒分子生物学特征。方法收集湖南省2013、2014年确诊的26例人感染H7N9禽流感病毒患者的资料,对人和禽分离的H7N9病毒进行鉴定和测序分析。结果26例患者中,发热和咳嗽是最常见的起病症状,所有患者均存在肺炎;20例(76.92%)出现急性呼吸窘迫综合征(ARDS),25例(96.15%)初诊时白细胞下降或正常,发病至开始进行抗病毒治疗的平均时间为10 d。10例死亡,病死率达38.46%。患者分离的H7N9病毒株测序分析表明,发生了H7基因Gln226Leu和Gly186Val替换,PB2基因Asp701Asn突变。结论急性呼吸系统损害是人感染H7N9禽流感的主要临床表现,活禽暴露是人感染H7N9禽流感的重要危险因素,H7N9禽流感病毒基因发生了部分位点的适应性突变,更容易从禽类向人跨种传播引起人类严重疾病,需加强病原学监测。     

2011 - 2015年宿迁市禽流感职业暴露人群和环境监测结果分析

摘要:目的 了解宿迁市职业暴露人群H5N1 禽流感病毒抗体水平和环境中禽流感病毒的分布情况,为禽流感防控提供科学依据。方法 在2011 - 2015年采集从事家禽养殖、屠宰等人群血清标本用血凝抑制试验检测H5N1 抗体;对在城乡活禽市场等采集的环境标本用Real-time PCR法检测禽流感病毒FluA、H5、H7、H9核酸。结果 职业暴露人群572人份血清A（H5N1）抗体均为阴性;1 038份环境标本共检出流感A型阳性标本65份,阳性率为6.26%（其中H5阳性率1.64%,H7阳性率0.19%,H9阳性率3.28%,A未分型0.48%,混合感染0.58%）。结论 职业暴露人群血清标本中未检测出A（H5N1）禽流感病毒抗体阳性标本;宿迁市监测点环境中存在H5、H7、H9 禽流感病毒,存在人感染高致病性禽流感的风险。禽流感感染风险主要集中在城乡活禽市场。     

人感染禽流感家庭聚集性病例研究进展

1997年以来,全球多个国家相继出现人感染H5N1禽流感家庭聚集性病例,随后中国局部地区也陆续报告了人感染H7N9禽流感相关病例。目前存在的人传人的现象是有限非持续的,具体的人际间传播途径与方式并不清楚且尚无证据证实上述2种病毒可以在人间持续传播。家庭聚集性病例多发生在与禽类接近或接触的人群中,可能存在的遗传易感性以及个体间受体表达的差异增加了家庭成员感染禽流感病毒的风险。随着人感染H5N1与H7N9禽流感病毒的持续流行以及病毒自身变异的发生,不排除其获得对人类的适应性突变可能性。人感染H7N9病例中未检测出的症状轻微感染者可能会引起更难以控制的人际间流行。本文将从人感染H5N1、H7N9病毒家庭聚集性病例的流行病学特征、传播模式以及传播能力等方面进行系统阐述,为今后禽流感疫情的防控提供一定的科学依据。     

嘉兴市外环境禽流感病毒污染状况及职业暴露人群H5N6、H7N9和H9N2抗体水平调查

目的 了解嘉兴市外环境禽流感病毒分布情况及涉禽职业暴露人群禽流感病毒感染现状,为科学有效防控人感染禽流感疫情提供科学依据。 方法 实时荧光定量PCR检测2013年3月-2016年4月采集的嘉兴市3 115份外环境标本的A型流感病毒核酸,并对A型流感病毒核酸阳性的标本进一步进行H5、H7、H9亚型检测。采用马血红细胞凝集抑制试验检测2015年4月和2016年4月采集的嘉兴市140名涉禽职业暴露人群血清中的H5N6、H7N9和H9N2血凝素抗体。 结果 外环境标本中A型流感病毒核酸阳性率为18.11%,H5、H9、H7亚型阳性率分别为0.64%、3.21%、5.07%;同时,外环境标本中检出不同亚型混合污染标本74份,且H9/H7混合污染的阳性率达到1.86%。A型流感病毒及H7亚型阳性率在冬春季节出现高峰,且在城乡活禽市场的阳性率明显高于其他场所;宰杀或摆放禽肉案板表面和清洗禽类的污水标本中A型流感病毒及H7亚型的阳性率明显高于其他标本类型。140份人群血清标本共检出H9N2抗体阳性标本5份,阳性率为3.57%,未检出H5N6、H7N9抗体阳性标本。 结论 2013-2016年嘉兴市外环境中存在H5、H9、H7亚型污染,且涉禽职业暴露人群中少量的H9N2禽流感病毒无症状感染者,提示禽类接触、活禽交易市场暴露有感染禽流感病毒风险,因此应做好重点人群的健康教育及重点区域的禽流感病毒监测,防止人感染禽流感疫情的发生。     

河南省首例人感染H7N9禽流感病例的流行病学调查

[目的]通过对1例人感染H7N9禽流感病毒患者的调查分析,为人感染H7N9禽流感的科学防控提供依据。[方法]采用流行病学调查方法,调查病例的发病经过、可能的感染来源、传播途径及暴露因素等,医学观察患者的密切接触者,同时对患者进行临床诊治、实验室检测。[结果]确诊1例人感染HTN9禽流感病毒,经救治后痊愈出院。患者有明确的活禽接触史,咽拭子检测H7N9禽流感病毒核酸阳性。患者的密切接触者中均未发现异常临床表现。通过扩大监测流感病例160例和职业人群858例,均未发现H7N9禽流感病毒核酸阳性。当地活禽交易市场鸡咽拭子标本检出2份H7N9禽流感病毒核酸阳性,阳性鸡来源于外省。[结论]活禽暴露是人感染H7N9禽流感病毒的关键风险因素,暂无证据人传人,未发现人群隐性感染和轻症病例。仍需开展扩大监测和流行病学调查,以完善对感染谱的认识。     

阳江市人感染H7N9禽流感监测与分析

目的了解人感染H7N9禽流感的流行态势,为该传染病的防控提供科学依据。方法开展流感样病例和严重急性呼吸道感染病例监测、职业暴露人群监测和活禽市场环境污染监测,采用RT-PCR方法检测流感和禽流感病毒核酸。结果截至2014年4月30日,阳江市累计报告人感染H7N9禽流感确诊病例4例,死亡2例;2013年12月16日至2014年4月30日,流感样病例就诊比例为4.30%;全市报告和采集标本的严重急性呼吸道感染病例128例,检出H7N9禽流感病毒核酸阳性3例;接受医学观察的186名从业人员未发现有人感染H7N9禽流感;采集环境标本1 188份,检出H7N9禽流感病毒核酸阳性78份,阳性率为6.57%;监测市场194个(次),检出有阳性标本的市场42个(次),市场阳性比例为21.65%。结论阳江市活禽市场环境污染严重且涉及范围广是导致病例发生的主要原因,加强活禽市场管理,严格落实清理消毒措施是控制疫情的有效方法。     

Infection with Possible Precursor of Avian Influenza A(H7N9) Virus in a Child,China, 2013

During the early stage of the avian influenza A(H7N9) epidemic in China in March 2013, a strain of the virus was identified in a 4-year-old boy with mild influenza symptoms. Phylogenetic analysis indicated that this strain, which has similarity to avian subtype H9N2 viruses, may represent a precursor of more-evolved H7N9 subtypes co-circulating among humans.     

Avian influenza A (H7N9) virus infection in humans: Epidemiology,evolution, and pathogenesis

New human influenza A virus strains regularly emerge causing seasonal epidemics and occasional pandemics. Lately, several zoonotic avian influenza A strains have been reported to directly infect humans. In early 2013, a novel avian influenza A virus (H7N9) strain was discovered in China to cause severe respiratory disease in humans. Since then, over 450 human cases of H7N9 infection have been discovered and 165 of them have died. Multiple epidemiological, phylogenetic, in vivo, and in vitro studies have been done to determine the origin and pathogenesis of novel H7N9 strain. This article reviews the literature related to the epidemiology, evolution, and pathogenesis of the H7N9 strain since its discovery in February 2013 till August 2014. The data available so far indicate that H7N9 was originated by a two-step reassortment process in birds and transmitted to humans through direct contact with live-bird markets. H7N9 is a low-pathogenic avian virus and contains several molecular signatures for adaptation in mammals. The severity of the respiratory disease caused by novel H7N9 virus in humans can be partly attributed to the age, sex, and underlying medical conditions of the patients. A universal influenza vaccine is not available, though several strain-specific H7N9 candidate vaccine viruses have been developed. Further, novel H7N9 virus is resistant to antiviral drug amantadine and some H7N9 isolates have acquired the resistance to neuraminidase-inhibitors. Therefore, constant surveillance and prompt control measures combined with novel research approaches to develop alternative and effective anti-influenza strategies are needed to overcome influenza A virus.     

Microbial adaptation and change: avian influenza

The evolution of influenza is a continuing process involving viral and host factors. The increasing frequency of emergence of the highly pathogenic H5N1, H7N3 and H7N7 influenza viruses and the panzootic spread of H9N2 influenza virus, all of which can be potentially transmitted to humans, are of great concern to both veterinary and human public health officials. The question is how soon the next pandemic will emerge. A convergence of factors, including the population densities of poultry, pigs and humans, are likely factors affecting the evolution of the virus. Highly concentrated poultry and pig farming, in conjunction with traditional live animal or 'wet' markets, provide optimal conditions for increased mutation, reassortment and recombination of influenza viruses. Strategies to reduce the evolution of influenza and the emergence of pandemics include the separation of species, increased biosecurity, the development of new vaccine strategies and better basic knowledge of the virus. More effective co-operation between scientists and veterinary and public health officials is required to achieve these goals.     

Clinical,epidemiological and virological characteristics of the first detected human case of avian influenza A(H5N6) virus

A human infection with novel avian influenza A H5N6 virus emerged in Changsha city, China in February, 2014. This is the first detected human case among all human cases identified from 2014 to early 2016. We obtained and summarized clinical, epidemiological, and virological data from this patient. Complete genome of the virus was determined and compared to other avian influenza viruses via the construction of phylogenetic trees using the neighbor-joining approach. A girl aged five and half years developed fever and mild respiratory symptoms on Feb. 16, 2014 and visited hospital on Feb. 17. Throat swab specimens were obtained from the patient and a novel reassortant avian influenza A H5N6 virus was detected. All eight viral gene segments were of avian origin. The hemagglutinin (HA) and neuraminidase (NA) gene segments were closely related to A/duck/Sichuan/NCXN11/2014(H5N1) and A/chicken/Jiangxi/12782/2014(H10N6) viruses, respectively. The six internal genes were homologous to avian influenza A (H5N2) viruses isolated in duck from Jiangxi in China. This H5N6 virus has not gained genetic mutations necessary for human infection and was suggested to be sensitive to neuraminidase inhibitors, but resistant to adamantanes. Epidemiological investigation of the exposure history of the patient found that a live poultry market could be the source place of infection and the incubation period was 2–5 days. This novel reassortant Avian influenza A(H5N6) virus could be low pathogenic in humans. The prevalence and genetic evolution of this virus should be closely monitored.     

北京市城区居民防控人感染H7N9禽流感认知分析

目的了解北京市中心城区居民对人感染H7N9禽流感疫情的认知情况,为北京市人感染H7N9禽流感疫情的防控工作提供参考。方法以北京市第六次人口普查的城区居民人口比例为基础,选择相应数量的老年人、中学生和中小学生的家长作为调查对象。采用整群抽样的方法随机抽取2400人,进行问卷调查。结果 91.9%的居民知晓H7N9禽流感病例如何传染,27.8%的居民知晓H7N9禽流感发病早期最主要症状,28.3%的居民知晓哪些人更容易感染H7N9禽流感;59.0%的居民在禽流感发生后洗手次数有所增加;男性对H7N9病例如何感染、传播途径、防控措施和易感人群的知晓率均低于女性（P〈0.01）。结论居民对H7N9流感的知识掌握普遍较好,但居民对H7N9禽流感的易感人群和发病早期的主要症状知晓率较低,相关部门还要加强这方面的宣传。H7N9禽流感病例如何感染、传播途径、防控措施和易感人群的相关知识传播还需向男性倾斜。在日常的健康教育中还需正确引导居民正确食用和加工禽类及其制品。     

湖南省2005-2017年人感染禽流感流行病学特征分析

目的 对湖南省发现的所有人感染禽流感病例进行流行病学特征分析，为防控策略的制定和调整提供科学依据。方法 对疫情概况、病例三间分布和暴露史进行描述，并报道家庭聚集性病例。结果 湖南省已发现人感染H5N1病例6例，人感染H5N6病例4例，人感染H7N9病例99例，人感染H9N2病例6例。病例主要发生在11月至次年4月。H5N1病例分布在5个市州，H5N6病例分布在4个市州，H9N2病例分布在3个市州，H7N9病例分布在13个市州。4种亚型人感染禽流感在男性和女性中均有发生。H5N1、H5N6和H9N2病例年龄较小，H7N9病例以中老年为主。51.0%的病例为农民。95.5%的病例有禽类或禽类污染的环境暴露史。湖南省已发现H5N1、H5N6疑似家庭聚集性病例和H7N9确诊家庭聚集性疫情。结论 禽类和禽类环境是人感染禽流感病毒的主要来源，开展环境监测有利于疾病的预测预警。禽流感病毒存在有限非持续的人传人现象，密切监测病毒基因变化，对密切接触者实行医学观察，对于防止二代病例发生有重要意义。     

北京市房山区人群禽流感病毒感染风险分析

目的评估北京市房山区人感染禽流感发生风险,为制定有效的防控措施提供科学依据。方法2017-04-23,对北京市房山区首例人感染H7N9禽流感病例感染来源进行调查,并通过疫情强化监测、禽流感血清学监测和禽流感外环境监测建立禽流感监测体系,对咽拭子标本和外环境标本进行禽流感病毒核酸检测,对血清标本进行抗体滴度检测,并进行χ~2检验,检验水准α=0.05。结果禽流感疫情调查提示病例感染来源于从流动商贩买的鸡。强化监测发现了1例H9N2禽流感确诊病例。采集血清标本455份,阳性44份(9.67%),其中阳性率最高为H5N6,其次为H9N2。野生候鸟栖息地人员禽流感血清抗体检测阳性率高于禽类、猪类从业人员,差异有统计学意义(χ^2=10.278,P<0.05)。禽流感及野禽外环境监测共采集标本960份,检出禽流感阳性标本13件(1.35%),全部源于活禽买卖宰杀摊位。禽咽拭子肛拭子阳性检出率最高,为27.78%,其次为宰杀或摆放禽肉案板表面涂抹样本,阳性率16.28%。结论北京市房山区发生了H7N9和H9N2禽流感疫情,禽流感环境监测和血清学监测均发现了禽流感病毒,流动活禽交易或宰杀是人群感染禽流感的主要风险来源。应加强农业、卫生、工商等部门联防联控,采取积极措施防控禽流感。     

2010-2012年南宁市职业暴露人群血清学和环境高致病性禽流感监测分析

目的了解南宁市职业暴露人群高致病性H5N1禽流感病毒的接触感染状况和南宁市及周边地区活禽市场、养殖厂等环境禽流感病毒H5、H7、H9亚型污染状况,为防治人禽流感提供科学依据。方法在2010-2012年采集从事家禽养殖、屠宰等人群血清标本用红细胞凝集抑制试验（HI）检测H5N1抗体;对在城乡活禽市场外环境采集的笼具涂抹、粪便和污水标本用荧光定量PCR法检测禽流感病毒FluA、HS、H7、H9核酸。结果共采集职业暴露人群80人份血清H5N1抗体均为阴性;环境标本175份禽流感病毒核酸监测阳性标本为47份,阳性率为26．86％。A型禽流感病毒核酸阳性标本分布于6个城区（县）的9个活禽农贸市场,各个季节采集的标本的阳性率有差异。3种类型的标本中,水的阳性率最高,其次是笼具涂抹标本,粪便的阳性率最低。结论禽流感H5亚型在南宁市职业暴露人群中未发现隐性感染;活禽市场环境普遍存在高致病性禽流感病毒的污染,H5和H9亚型是主要的病原体。     

1起人感染H7N9禽流感家庭聚集性疫情的流行病学调查

目的 针对吉安市发生的首起人感染H7N9禽流感家庭聚集性疫情开展流行病学调查,探索可能的感染来源,为人感染禽流感病毒疫情的防控提供科学依据。方法 采用描述性流行病学方法对2名病例及其密切接触者开展流行病学调查,并采集其相关呼吸道标本,采用RT PCR方法开展H7N9病毒核酸检测。结果 首例患者于2016年4月1日发病,17日确诊,被感染的途径为活禽市场暴露和与禽类接触;其母亲4月5日发病,17日确诊,被感染的可能途径有2种:（1）禽肉处理;（2）母亲与首例病例的密切接触。经过对患者的积极处置和救治,2名患者已出院,此次疫情得到有效的控制。结论 此次疫情所涉及的2例病例确认为人感染H7N9禽流感家庭聚集性病例,首发病例通过禽类暴露而感染,续发病例因共同暴露感染可能性大,但无法完全排除有限人传人的可能性。     

江西省人感染禽流感病例流行病学特征分析

目的 分析江西省不同亚型人感染禽流感病例的流行特征,为江西省禽流感防控策略的制定和优化提供科学依据。方法 以江西省2013年1月至2016年4月报告的人感染禽流感确诊病例为研究对象,采用流行病学个案调查方法,分析病例的流行病学特征。结果 江西省共报告人禽流感确诊病例18例,其中H7N9病例14例,H10N8病例3例,H5N6病例1例;死亡4例,病死率22.22%。88.89%（16/18）的病例发生在1 - 2、4和12月,61.11%（11/18）的病例出现在鄱阳湖周边地区;病例年龄中位数为62岁（23～80岁）,男性占55.56%（10/18）;17例病例均有明确的禽类暴露史,病例可疑暴露场所环境相关标本中H7N9、H10N8禽流感病毒阳性标本检出率分别为12.24%和5.19%。结论 江西省人感染禽流感病例在冬春季高发,且存在一定的地域集聚性,多数病例发病前有禽类或活禽市场暴露史。建议实施“加强活禽市场管理,控制发病风险”控制措施,并主动开展禽流感病毒病原学监测和血清学调查,系统收集轻症病例和隐性感染者信息,全面分析和掌握我省人禽流感流行特征,为科学防控人禽流感疫情提供依据。     

Genomic Signatures of Influenza A Pandemic (H1N1) 2009 Virus

Adaptive mutations that have contributed to the emergence of influenza A pandemic (H1N1) 2009 virus, which can replicate and transmit among humans, remain unknown. We conducted a large-scale scanning of influenza protein sequences and identified amino acid–conserving positions that are specific to host species, called signatures. Of 47 signatures that separate avian viruses from human viruses by their nonglycoproteins, 8 were human-like in the pandemic (H1N1) 2009 virus. Close examination of their amino acid residues in the recent ancestral swine viruses of pandemic (H1N1) 2009 virus showed that 7 had already transitioned to human-like residues and only PA 356 retained an avian-like K; in pandemic (H1N1) 2009 virus, this residue changed into a human-like R. Signatures that separate swine viruses from human viruses were also present. Continuous monitoring of these signatures in nonhuman species will help with influenza surveillance and with evaluation of the likelihood of further adaptation to humans.     

A vaccine prepared from a non-pathogenic H5N1 avian influenza virus strain confers protective immunity against highly pathogenic avian influenza virus infection in cynomolgus macaques

In order to prepare for the emergence of pandemic influenza viruses, we have established an influenza virus library that contains non-pathogenic influenza A virus strains with 135 combinations of 15 hemagglutinin and 9 neuraminidase subtypes. In this study, we developed a vaccine against H5N1 highly pathogenic avian influenza (HPAI) virus infection in humans using a virus strain selected from the library. We examined its immunogenic potency using cynomolgus macaques as a primate model. Virus antigen-specific antibodies were elicited by intranasal or subcutaneous administration of inactivated whole virus particle vaccines. After challenge with an H5N1 HPAI virus isolate obtained from a Vietnamese patient, the virus was detected only on next day following inoculation in the nasal and/or tracheal swabs of vaccinated macaques that were asymptomatic. On the other hand, the viruses were isolated from nasal and tracheal swabs from non-vaccinated macaques until day 5 and day 7 after inoculation of the H5N1 HPAI virus, respectively. Although six non-vaccinated macaques developed a high body temperature, and two of them lost their appetite after HPAI virus infection, they recovered by the end of the 12-day observation period and did not show the severe symptoms that have been reported in human H5N1 virus infection cases. This demonstrates that the vaccine prepared with the non-pathogenic H5N1 virus from our influenza virus library conferred protective immunity against H5N1 HPAI virus infection to macaques.     

Recent zoonoses caused by influenza A viruses

Influenza is a highly contagious, acute illness which has afflicted humans and animals since ancient times. Influenza viruses are part of the Orthomyxoviridae family and are grouped into types A, B and C according to antigenic characteristics of the core proteins. Influenza A viruses infect a large variety of animal species, including humans, pigs, horses, sea mammals and birds, occasionally producing devastating pandemics in humans, such as in 1918, when over twenty million deaths occurred world-wide. The two surface glycoproteins of the virus, haemagglutinin (HA) and neuraminidase (NA), are the most important antigens for inducing protective immunity in the host and therefore show the greatest variation. For influenza A viruses, fifteen antigenically distinct HA subtypes and nine NA subtypes are recognised at present; a virus possesses one HA and one NA subtype, apparently in any combination. Although viruses of relatively few subtype combinations have been isolated from mammalian species, all subtypes, in most combinations, have been isolated from birds. In the 20th Century, the sudden emergence of antigenically different strains in humans, termed antigenic shift, has occurred on four occasions, as follows, in 1918 (H1N1), 1957 (H2N2), 1968 (H3N2) and 1977 (H1N1), each resulting in a pandemic. Frequent epidemics have occurred between the pandemics as a result of gradual antigenic change in the prevalent virus, termed antigenic drift. Currently, epidemics occur throughout the world in the human population due to infection with influenza A viruses of subtypes H1N1 and H3N2 or with influenza B virus. The impact of these epidemics is most effectively measured by monitoring excess mortality due to pneumonia and influenza. Phylogenetic studies suggest that aquatic birds could be the source of all influenza A viruses in other species. Human pandemic strains are thought to have emerged through one of the following three mechanisms: genetic reassortment (occurring as a result of the segmented genome of the virus) of avian and human influenza A viruses infecting the same host direct transfer of whole virus from another species the re-emergence of a virus which may have caused an epidemic many years earlier. Since 1996, the viruses H7N7, H5N1 and H9N2 have been transmitted from birds to humans but have apparently failed to spread in the human population. Such incidents are rare, but transmission between humans and other animals has also been demonstrated. This has led to the suggestion that the proposed reassortment of human and avian viruses occurs in an intermediate animal with subsequent transference to the human population. Pigs have been considered the leading contender for the role of intermediary because these animals may serve as hosts for productive infections of both avian and human viruses and, in addition, the evidence strongly suggests that pigs have been involved in interspecies transmission of influenza viruses, particularly the spread of H1N1 viruses to humans. Global surveillance of influenza is maintained by a network of laboratories sponsored by the World Health Organization. The main control measure for influenza in human populations is immunoprophylaxis, aimed at the epidemics occurring between pandemics.     

Mutations of Novel Influenza A(H10N8) Virus in Chicken Eggs and MDCK Cells

The recent emergence of human infection with influenza A(H10N8) virus is an urgent public health concern. Genomic analysis showed that the virus was conserved in chicken eggs but presented substantial adaptive mutations in MDCK cells. Our results provide additional evidence for the avian origin of this influenza virus.