2005～2006年宁波市流行性感冒病毒的流行与优势株转换分析

目的：分析2005—2006年宁波市流行性感冒病毒的流行与流感病毒优势株的转换情况。方法：常年监测宁波市流感病毒的流行情况，选取不同时间的各种型别流感毒株进行血凝素基因HA1区核苷酸序列测定，并推导出其氨基酸序列进行基因进化特性分析。结果：2005年1—9月份宁波市的甲型流感以H3N2亚型为流行优势株，而乙型流感在2005年初以Yamagata系占优势。到2005年9月份以后至2006年底甲型流感的H1N1亚型替代了H3N2亚型占据优势株地位，乙型流感也以Victoria系成了优势株。结论：在2005年流感病毒甲、乙型的流行株均发生了亚型或种系的优势转换。流行株的基因特征及抗原性发生了明显的变异，并造成了一定规模的暴发流行。     

中国2000～2001年流行性感冒流行概况

目的：了解中国2000－2001年流行性感冒（流感）流行及抗原性变异情况。方法：鸡胚传代病毒用于抗原分析；病毒液提取RNA进行逆转录－聚合酶链反应（RT－CR），扩增产物纯化后测序。然后用MegAlign(Version1.03）和Editseq（Version3．69）软件进行基因种系发生树分析。结果：2001年流行的H1N1亚型病毒血凝素蛋白重链（H1N1）相比，在抗原决定簇D区的190位发生了氨基酸替换；基因种系发生树表明2001年的H1N1亚型流感病毒存在基因特性不同的两系病病毒株，国内人群中仍然同时流行着两种抗原性明显不同的B型流感病毒（Yamagata系和Victoria系），Yamagata系病毒占大多数，Version系的HA1区基因与B／山东／7／97毒株相比，其197和199位氨基酸发生了替换。B型的基因种系发生树也证实Version系病毒株的抗原性改变。2000年分离的H3N2亚型流感病毒的HA1区氨基酸序列与A／悉尼／5／97（H3N2）间有7－8个氨基酸的差异；2001年分离的H3N2病毒株与2000年的病毒株相比，又有83、186、202、222位发生了氨基酸替换，表明H3N2亚型病毒株间的抗原性发生了较明显的变异。结论：2000－2001年中国流感的流行情况较为平静；H3N2亚型的抗原性发生了变异，H1N1亚型和B型病毒的抗原性虽没有发生明显的变异，但它们均同时流行着两系抗原性不同的毒株。     

广东省2003年甲3型流行性感冒病毒血凝素重链区基因的特征

目的了解广东省2003年甲型流行性感冒(流感)病毒的抗原变异情况和血凝素重链区(HA1)基因的特征.方法对广东省流感分子流行病学资料进行分析.结果全年分离到481株甲型流感病毒,全部是H3N2亚型,其抗原性与疫苗株甲/马拿马/2007/99(H3N2)有所不同,类似于疫苗变异株甲/福建/411/02(H3N2).在HA1区氨基酸序列上,与疫苗株甲/巴拿马/2007/99(H3N2)存在25～30个氨基酸的差异,同源性为92.1%.抗原决定族A、B、D、E区以及受体结合部的左侧臂和前臂均发生氨基酸替换,并在144位增加了1个糖基化位点.结论广东省2003年甲3型流感活动比2002年进一步加强,与疫苗株相比,病毒基因发生突变,抗原性发生了漂移.     

2005-2006年河北省流感病毒监测与毒株变异分析

目的分析2005～2006年河北省流感病毒的流行与毒株变异情况。方法将采集的咽拭子标本用MDCK（Madin—Darby Canine Kidney）细胞培养分离流感病毒，血凝抑制试验鉴定病毒型别；在分离得到的3种型别流感病毒中分别以不同时间点选取分离株，进行血凝素重链（HA1）区核苷酸序列测定，并进行基因进化特性分析。结果2005～2006年分离到流感病毒92株，甲1亚型57株，甲3亚型6株，乙型29株。HA1区核苷酸和氨基酸序列分析表明，甲1亚型流感病毒与A／New Caledonia／20／99比较，1株有5个位点（173V〉A、259W〉R、260Y〉F、281 E〉K、322V〉A）发生氨基酸替换，2株有7个位点（90T〉K、102Y〉H、153R〉K、173V〉A、216R〉K、259W〉R、274T〉N）发生替换。3株甲3亚型与A圯alfornia／7／2004比较3个位点（188N〉D、193S〉F、225D〉N）氨基酸发生同样的替换。3株乙型流感病毒与B／HongKong／330／2001比较有7个位点（48K〉E、80K〉R、116R〉H、121N〉T、129K〉N、164E〉D、197S〉N）发生了相同的氨基酸替换。结论2005～2006年河北省流行甲1、甲3亚型和乙型流感病毒。流行株的基因特性发生了一定程度的变异，但乙型毒株变异更明显。     

北京流感暴发流行前后流行株的分离和抗原性分析

目的：为获得1998年12月北京流感暴发前和后的流行株,并了解流行株的抗原变异幅度。方法：应用常规法进行流感病毒分离,应用血凝抑制免疫交叉试验（HI）,以6株国际参考株和2株国家代表株,对流行株作抗原性分析。结果：共获甲3亚型（H3N2）流行株15株,它们的抗原性与A3／南非／1147／96、A3／悉尼／05／97、A3／日本／8／98、A3／智利／3792／98、A3／阿根廷／413／98均有明显差异。它们与国家代表株A3／山东／9／93的抗原性也有差异,但与A3／南昌／933／95和A3／汉防／359／95两株的抗原性无明显差异。结论：所分离到的15 均为甲3亚型流感毒株（H3N2）,是北京1998年的流行优势株;同时也证实1998年12月北京流感暴发流行的病毒主要也是H3N2亚型毒株。它们的抗原性与国际参考株：南非、悉尼、日本、智利、阿根廷有明显差异。应用国际流感疫苗效果不佳的重要原因在于甲3亚型流行株与A3／悉尼／05／95国际代表株抗原性不大对应。     

2005～2006年流感季节河北省甲3亚型流感病毒血凝素重链区基因变异分析

目的：研究2005～2006年流感流行期河北省分离的甲3（H3N2）亚型流感病毒株血凝素重链（HA1）的基因特性,了解H3N2亚型流感病毒株HA1基因的变异及其与流感流行的关系。方法：用狗肾（MDCK）细胞分离培养流感病毒,提取病毒核糖核酸（RNA）,采用RT-PCR法扩增病毒HA1基因,纯化产物进行核苷酸序列测定,用DNAStar软件作分析处理。结果：2005～2006年流感流行期在河北省分离到的H3N2亚型流感病毒株HA1与同时期的H3N2亚型流感疫苗株A/Calfornia/7/04相比其抗原性变异不大,核苷酸同源性为96.2%～98.2%,氨基酸同源性为98.7%～99.0%,3个位点发生了氨基酸替换,其中2个在抗原决定簇B区（188N〉D、193S〉F）,1个在受体结合位点（225D〉N）。结论：H3N2亚型流感病毒HA1尚未发生明显变异,与疫苗株同源性较高。人群对其已建立起较好的免疫屏障,这是河北省该流行期H3N2亚型活动水平低的主要原因。     

2007-2009年郴州市H3N2亚型流感病毒HA1基因特性研究

目的了解2007-2009年郴州市H3N2亚型流感病毒流行情况及血凝素基因变异特征。方法 按时间先后顺序随机选择2007-2009年流感病原学监测中分离到的H3N2亚型毒株8株,提取病毒核糖核酸（RNA）,采用RT-PCR法扩增病毒HA1基因,纯化产物进行核苷酸序列测定并推导其氨基酸序列进行基因特性分析。结果H3N2亚型流感病毒在2007年为优势株,2008-2009年相对H1N1亚型流感病毒为弱势株;2007年分离株与该年疫苗株（A/Wisconsin/67/2005）比较,变异位点主要为G50E、S138A、K140I、R142G、N144D和L157S,抗原性发生了漂移;2008年分离株与2008-2009年疫苗株（A/Brisbane/10/2007）比较,变异位点主要为R142G、L157S;2009年分离株与该年疫苗株比较,变异位点主要为L157S、K173Q,2008-2009年分离株与该年疫苗株比较未发生明显变异。结论郴州市2007年H3N2亚型流感病毒HA1发生了明显变异,H3N2流感病毒较活跃,当年生产的疫苗预防效果较差;2008-2009年H3N2亚型流感病毒HA1与该年度疫苗株相比未发生明显变异,人群对其建立较好的免疫屏障,这是郴州市2008-2009年H3N2亚型流感病毒活动水平较低的主要原因。     

北京地区2005～2006年流感病原监测结果与乙型流感病毒HA1序列分析

目的：分析2005～2006年冬春季北京地区流感病原监测及乙型流感病毒种系分布情况。方法：采用狗肾传代细胞（MDCK）和鸡胚培养分离流感病毒，经血清学试验鉴定分型。选取部分乙型流感提取病毒RNA，经RT—PCR扩增得到HA1基因片段并进行核苷酸序列测定，用信息软件进行种系发生树分析。结果：共采集流感样病例标本1874份，经MDCK细胞分离到510株流感病毒。其中H1N1亚型244株（47．84％）；H3N2亚型57株（11．18％）；B型209株（40．98％），208株为Victoria系，1株为Yamagata系。对210份细胞分离阳性标本进行鸡胚培养，共分离到流感病毒9株，全部为H1N1亚型。28株B型优势流行株与当年疫苗株不属于同一谱系，相差较远；与新预测（2006～2007年）的疫苗株亲缘关系最近。结论：北京地区2005～2006年冬春季节存在H1N1、H3N2、B型3种流感病毒流行，以H1N1、B型为优势毒株。B型Victoria系优势株正在通过变异逐步在流行中占据主导地位。新预测流感疫苗可对人群产生良好的保护效果。     

1991～2000年广东省流感监测结果分析

目的 了解流感流行和流感病毒毒株表面抗原性变异情况。方法 用9～11d龄鸡胚和(或)麦克丁氏犬肾(MDCK)细胞分离流感病毒，病毒鉴定用常量红细胞凝集抑制法(HI)；鸡血清流感抗体检测采用微量半加敏红细胞凝集抑制法(HI)。结果 1991～2000年全省未发生流感大流行。期间从人群中共分离流感病毒1008株，以A(H3N2)亚型流感病毒(62．3％)、B型流感病毒(26．6％)为主。从人群中分离出10株H9N2亚型禽流感病毒。从鸡群中分离到H9N2亚型禽流感病毒98株。A(H3N2)亚型病毒的抗原性不断发生漂移。结论 除1993、1995年未分离到A(H1N1)亚型流感病毒外。其它8年均分离到A(H1N1)、A(H3N2)、B型流感病毒。1998、1999年还同时分离到H9N2亚型禽流感病毒。并证实了A(H3N2)亚型病毒表面抗原的易变性；鸡群中有多个A亚型流感病毒同时存在，必须做好流感监测。     

1991～1995年广东省流感病毒分离概况

1991－1995年，我省流感病毒分离情况详见表1。1991年的病毒以甲1（H1N1）型占优势。1992、1993、1995年均以甲3（H3N2）型占优势。1994年以乙型流感病毒占优势。1991年夏天，以甲1（H1N1）型病毒感染所致散发病例为主，秋天，即以乙型病毒散发病例为主，1992－1993年甲3（H3N2）型病毒较活跃，夏季多为甲3（H3N2）型病毒感染，秋季即乙型病毒感染较多。1994年春，乙型流感较活跃，夏天，除了乙型病毒继续传播外，也有甲1和甲3型病毒混合感染。五年来甲1（HINI）亚型病毒抗原性非常稳定，抗原性仍类似于甲1／京防86－1。甲3（H3NZ）…     

Predominance of influenza virus A(H3N2) 3C.2a1b and A(H1N1)pdm09 6B.1A5A genetic subclades in the WHO European Region, 2018–2019

BackgroundThe 2018/2019 influenza season in the WHO European Region was dominated by influenza A (H1N1)pdm09 and (H3N2) viruses, with very few influenza B viruses detected.MethodsCountries in the European Region reported virus characterization data to The European Surveillance System for weeks 40/2018 to 20/2019. These virus antigenic and genetic characterization and haemagglutinin (HA) sequence data were analysed to describe and assess circulating viruses relative to the 2018/2019 vaccine virus components for the northern hemisphere.ResultsThirty countries reported 4776 viruses characterized genetically and 3311 viruses antigenically. All genetically characterized A(H1N1)pdm09 viruses fell in subclade 6B.1A, of which 90% carried the amino acid substitution S183P in the HA gene. Antigenic data indicated that circulating A(H1N1)pdm09 viruses were similar to the 2018/2019 vaccine virus. Genetic data showed that A(H3N2) viruses mostly fell in clade 3C.2a (75%) and 90% of which were subclade 3C.2a1b. A lower proportion fell in clade 3C.3a (23%) and were antigenically distinct from the vaccine virus. All B/Victoria viruses belonged to clade 1A; 30% carried a double amino acid deletion in HA and were genetically and antigenically similar to the vaccine virus component, while 55% carried a triple amino acid deletion or no deletion in HA; these were antigenically distinct from each other and from the vaccine component. All B/Yamagata viruses belonged to clade 3 and were antigenically similar to the virus component in the quadrivalent vaccine for 2018/2019.ConclusionsA simultaneous circulation of genetically and antigenically diverse A(H3N2) and B/Victoria viruses was observed and represented a challenge to vaccine strain selection.     

Influenza activity in China: 1998-1999

During 1989-1999, influenza A H3N2 and H1N1 subtypes and B type viruses were still co-circulating in human population in China, while influenza A (H3N2) virus was predominant strain. The two antigenically and genetically distinguishable strains of influenza B virus were also still co-circulating in men in southern China. The antigenic analysis indicated that most of the H3N2 viruses were A/Panama/2007/99 (H3N2)-like strain, the most of the H1N1 viruses were antigenically similar to A/Beijing/262/95 (H1N1) virus. However, most of the influenza B viruses were B/Beijing/184/93-like strain, but few of them were antigenically similar to B/Shandong/7/97 virus. In the summer of 1998, the influenza outbreaks caused by H3N2 subtype of influenza A virus occurred widely in southern China. Afterwards, during 1998-1999 influenza season, a severe influenza epidemic caused by H3N2 virus emerged in northern China. The morbidity was reached as high as 10% in Beijing area. It was interesting that during influenza, surveillance from 1998 to 1999, five strains of avian influenza A (H9N2) virus were isolated from outpatients with influenza-like illness in July-August of 1998, and another one was repeatedly isolated from a child suffering from influenza-like disease in November of 1999 in Guangdong province. The genetic analysis revealed that the five strains isolated in 1998 were genetically closely related to H9N2 viruses being isolated from chickens (G9 lineage virus), whereas, A/Guangzhou/333/99 (H9N2) virus was a reassortant derived from reassortment between G9 and G1 lineage of avian influenza A (H9N2) viruses due to its genes encoding the HA, NA, NP and NS proteins, closely related to G9 lineage virus, the rest of the genes encoding the M and three polymerase (PB2, PB1 and PA) were closely related to G1 lineage strain of H9N2 virus. However, no avian influenza A (H5N1) virus has so far been isolated neither from in or outpatients with influenza-like disease in mainland China. Unfortunately, where did the reassortment occur and how did the reassortant transmit to men? These questions are still unknown.     

Annual report of the National Influenza Surveillance Scheme, 2003.

Surveillance of influenza in Australia is based on laboratory isolation of influenza viruses, sentinel general-practitioner practices for influenza-like illness, and absenteeism data from a major national employer. In 2003, the peak in influenza activity was in August which was later than in 2002. In 2003, 3,604 laboratory-confirmed cases of influenza were notified to the National Notifiable Diseases Surveillance System, which was marginally lower than for the previous year. Ninety-four per cent of the circulating viruses were influenza A. This was the highest proportion in the last five years. Nine hundred and thirty-five isolates were antigenically analysed: 928 were A(H3), two were A(H1) strains and five were influenza B viruses. The majority (98%) of the A(H3) subtypes were A/Fujian/411/2002(H3N2)-like and have shown a significant antigenic drift. The 2003 Australian influenza vaccine contained A/Panama/2007/99, which induced 2-4-fold lower antibody response against the drifted strain. An A/Fujian/411/2002(H3N2)-like virus has been incorporated in the Australian influenza vaccine for 2004. In 2003, the influenza vaccine was given to 77 per cent of Australians aged over 65 years; the same up take as in 2002.     

Antigenic and genetic characterization of influenza viruses circulating in Bulgaria during the 2015/2016 season

Influenza virological surveillance is an essential tool for early detection of novel genetic variants of epidemiologic and clinical significance. The aim of this study was to determine the antigenic and molecular characteristics of influenza viruses circulating in Bulgaria during the 2015/2016 season. The season was characterized by dominant circulation of A(H1N1)pdm09 viruses, accounting for 66% of detected influenza viruses, followed by B/Victoria-lineage viruses (24%) and A(H3N2) viruses (10%). All sequenced influenza A(H1N1)pdm09, A(H3N2) and B/Victoria-lineage viruses belonged to the 6B.1, 3C.2a and 1A genetic groups, respectively. Amino acid analysis of 57 A(H1N1)pdm09 isolates revealed the presence of 16 changes in hemagglutinin (HA) compared to the vaccine virus, five of which occurred in four antigenic sites, together with 16 changes in neuraminidase (NA) and a number of substitutions in proteins MP, NP, NS and PB2. Despite the many amino acid substitutions, A(H1N1)pdm09 viruses remained antigenically closely related to A/California/7/2009 vaccine virus. Bulgarian A(H3N2) strains (subclade 3C.2a) showed changes at 11 HA positions four of which were located in antigenic sites A and B, together with 6 positions in NA, compared to the subclade 3C.3a vaccine virus. They contained unique HA1 substitutions N171K, S312R and HA2 substitutions I77V and G155E compared to Bulgarian 3C.2a viruses of the previous season. All 20 B/Victoria-lineage viruses sequenced harboured two substitutions in the antigenic 120-loop region of HA, and 5 changes in NA, compared to the B/Brisbane/60/2008 vaccine virus. The results of this study reaffirm the continuous genetic variability of circulating seasonal influenza viruses and the need for continued systematic antigenic and molecular surveillance.     

Annual report of the National Influenza Surveillance Scheme, 2006

Influenza surveillance in Australia is based on laboratory isolation of influenza viruses, sentinel general practitioner reports of influenza-like illness, and absenteeism data from a major national employer. In 2006, 3,130 cases of laboratory-confirmed influenza were reported to the National Notifiable Diseases Surveillance System, which was one-third lower than in 2005. The influenza season started in mid-June, with peak activity in late August. Influenza A was the predominant type notified (71%), however influenza B activity continued to increase as a proportion of reported cases. Reports of influenza-like illness from sentinel general practitioners showed a slow but steady increase throughout the first half of the year to peak in late August. In 2006, 657 influenza isolates from Australia were antigenically analysed: 402 were A(H3N2), 24 were A(H1N1) and 231 were influenza B viruses. Continued antigenic drift was seen with the A(H3N2) viruses from the previous reference strains (A/California/7/2004 and A/New York/55/2004) and drift was also noted in some of the A(H1N1) strains from the reference/ vaccine strain A/New Caledonia/20/99, although very few A(H1N1) viruses were isolated in Australia in 2006. The B viruses isolated were predominately of the B/Victoria-lineage and similar to the reference/vaccine strain B/Malaysia/2506/2004.     

一起由H3N2流感病毒引起的局部流感暴发的病原学研究

目的 对一起流感局部暴发的病原体进行分离并鉴定，研究其变异情况，为流感的预防和控制提供依据。方法 用MDCK细胞对病人的咽拭标本进行分离培养，并对分离到的流感病毒HAl基因核苷酸序列进行测定及抗原分析。还检测了患者的血清抗体水平。结果在22份病人的咽拭标本中，分离到3株H3N2亚型流感病毒，患者恢复期血清抗体水平较急性期抗体水平升高4倍。将其中1株的HAl基因测序，与国际代表株进行比较，并与国际代表株进行交叉血抑试验，表明分离到的流感病毒发生抗原漂移。结论这种变异具有流行病学意义，造成甲3亚型流感病毒在湛江地区的局部暴发。     

Annual report of the National Influenza Surveillance Scheme, 2001.

Surveillance of influenza in Australia in 2001 was based on data from national and state-based sentinel practice consultations for influenza-like illness, laboratory isolations of influenza virus and absenteeism rates from a national employer. In 2001, laboratory-confirmed influenza became a notifiable disease and was reported to the National Notifiable Diseases Surveillance System (NNDSS). Influenza A was the dominant type, 81 per cent of which were subtype H1N1 and 19 per cent were subtype H3N2. The influenza A (H1N1) analysed were all A/New Caledonia/20/99-like strains. The H3N2 isolates were antigenically similar to the reference strain A/Moscow/10/99 and the vaccine strain A/Panama/2007/99. The influenza B isolates, which made up only 10 per cent of all isolates, were mainly B/Sichuan/379/99-like strains but 10 per cent of isolates were more closely related to B/Harbin/7/94-like viruses, which circulated in previous years. The Australian 2001 influenza vaccine represented a good match for the circulating viruses and 77 per cent of persons over 65 years in Australia were vaccinated in 2001.     

Antigenic and genetic characterization of current influenza strains

Annually the influenza centre receives more than 1000 virus isolates from around the world to monitor the changing pattern of viruses causing influenza throughout the year. These are characterized antigenically using both polyclonal and monoclonal antibodies and selected viruses are subjected to closer scrutiny by nucleotide sequence analyses of their HA genes. This information is used in making the annual recommendation of vaccine composition. As in the last 15 years, influenza A viruses of both H3N2 and H1N1 subtypes and influenza B viruses have been isolated during the recent influenza season. Outbreaks in the northern hemisphere were largely caused by influenza B viruses which are similar to the B/Panama/45/90 reference strain. The proportion of influenza A increased later in the season and was predominantly of the H3N2 subtype, viruses similar to the recent A/Beijing/32/92 variant being most prevalent. The observed changes taking place will be discussed in the context of recent trends.     

Antigenic sites of H1N1 influenza virus hemagglutinin revealed by natural isolates and inhibition assays

The antigenic sites of hemagglutinin (HA) are crucial for understanding antigenic drift and vaccine strain selection for influenza viruses. In 1982, 32 epitope residues (called laboratory epitope residues) were proposed for antigenic sites of H1N1 HA based on the monoclonal antibody-selected variants. Interestingly, these laboratory epitope residues only cover 28% (23/83) mutation positions for 9 H1N1 vaccine strain comparisons (from 1977 to 2009). Here, we propose the entropy and likelihood ratio to model amino acid diversity and antigenic variant score for inferring 41 H1N1 HA epitope residues (called natural epitope residues) with statistically significant scores according to 1572 HA sequences and 197 pairs of HA sequences with hemagglutination inhibition (HI) assays of natural isolates. By combining both natural and laboratory epitope residues, we identified 62 (11 overlapped) residues clustered into five antigenic sites (i.e., A-E) which are highly correlated to the antigenic sites of H3N2 HA. Our method recognizes sites A, B and C as critical sites for escaping from neutralizing antibodies in H1N1 virus. Experimental results show that the accuracies of our models are 81.2% and 82.2% using 41 and 62 epitope residues, respectively, for predicting antigenic variants on 197 paring HA sequences. In addition, our model can detect the emergence of epidemic strains and reflect the genetic diversity and antigenic variant between the vaccine and circulating strains. Finally, our model is theoretically consistent with the evolution rates of H3N2 and H1N1 viruses and is often consistent to WHO vaccine strain selections. We believe that our models and the inferred antigenic sites of HA are useful for understanding the antigenic drift and evolution of influenza A H1N1 virus.