Analysis of influenza A virus reinfection in children in Japan during 1983-91.

The epidemiology of influenza A in Japan was studied during 1979-91 and viruses isolated from reinfections during 1983-91 were analysed. Of 2963 influenza viruses isolated from reinfections during 1983-91 were analysed. Of 2963 influenza viruses isolated during this period, 922 and 1006 were influenza A(H1N1) and A(H3N2) viruses respectively; the others were influenza B viruses. Influenza A(H1N1) and A(H3N2) caused 5 and 6 epidemics respectively, most accompanied by antigenic drift. Seventeen reinfections with H1N1 and 17 with H3N2 were detected during our study. The primary and reinfection strains isolated from 7 H1N1 and 10 H3N2 cases were studied by haemagglutination-inhibition, and amino acid and nucleotide sequences of the HA1 region of the haemagglutinin. Most of the primary and reinfection strains were antigenically and genetically similar to the epidemic viruses circulating at that time. However, in 4 out of 10 cases of reinfection with influenza H3N2 virus, reinfection strains were genetically different from the epidemic viruses.     

Laboratory-based surveillance of influenza A(H1N1) and A(H3N2) viruses in 1980-81: antigenic and genomic analyses

During 1981, the A/Brazil/11/78-like strains of influenza virus that had been prevalent from 1978 to 1980 were displaced by a new set of heterogeneous, but closely related, variants (reference strain, A/England/333/80). Genomic analysis revealed that these new variants were almost exclusively nonrecombinant H1N1 viruses, i.e., they contained no genes of H3N2 origin. However, a few recombinant viruses containing the new variant HA and genes of H3N2 origin were identified. Antigenic analysis of H3N2 viruses indicated that they were also heterogeneous. The majority of these virus isolates were antigenically intermediate between A/Texas/1/77 and A/Bangkok/1/79, but additional variants were detected. Genomic analysis revealed that the H3N2 viruses isolated in the winter of 1980-81 were quite similar to H3N2 viruses isolated from 1977-79 in their T₁ oligonucleotide maps. No H1N1 genes were detected in H3N2 virus isolates. Comparison of pairs of oligonucleotide maps of total virus RNA indicated that a similar rate of genetic change had occurred for nonrecombinant H1N1 viruses, for recombinant H1N1 viruses, and for H3N2 viruses and that, in general, pairs of viruses exhibited increasing numbers of changes in their oligonucleotide maps as the time interval between isolation of the viruses increased.     

Laboratory-based surveillance of influenza virus in the United States during the winter of 1977-1978. I. Periods of prevalence of H1N1 and H3N2 influenza A strains, their relative rates of isolation in different age groups, and detection of antigenic variants

Influenza A (H3N2) viruses were isolated from outbreaks and epidemics of disease during the period December 1977 to March 1978. For the last two months of this period, H1N1 strains of influenza A were also responsible for epidemics. In some regions (e.g., Hawaii) co-circulation of H1N1 AND H3N2 strains occurred, whereas in other regions (e.g., Wisconsin) isolation of H3N2 strains had almost ceased prior to isolation of H1N1 strains. Few influenza B isolates were reported. Analysis of the ages of patients from whom specimens were submitted for influenza virus isolation confirmed that, whereas H3N2 strains were isolated from persons of all ages, greater than 97 per cent of H1N1 isolates in six states analyzed were recovered from patients less than 26 years old, although specimens were tested from older persons who were ill during the period of prevalence of H1N1 influenza. The majority of H3N2 isolates tested by hemagglutinin-inhibition reaction were similar to A/Texas/1/77, and the majority of H1N1 isolates were similar to A/USSR/90/77. Antigenic analysis of isolates, however, identified a small number of variants of H3N2 and H1N1 strains.     

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.     

The 2009 pandemic H1N1 virus induces anti-neuraminidase (NA) antibodies that cross-react with the NA of H5N1 viruses in ferrets

A miniaturized neuraminidase inhibition (NI) assay using HA-mismatched H6 reassortant viruses was performed to examine the neuraminidase (NA)-specific antibody response in ferrets immunized with live-attenuated influenza vaccine (LAIV) strains. The strains tested possessed different NAs derived from seasonal H1N1 and H3N2, 2009 pandemic H1N1, and the highly pathogenic influenza H5N1 virus. The anti-NA antibodies from the 2009 pandemic strain (A/California/7/2009) immunized ferrets cross-reacted with the NA of H5N1 but not with the NA of seasonal H1N1 viruses. The plaque size reduction assay confirmed the cross-reactivity between the NAs of A/California/7/2009 and the H5N1 virus. Sequence and structural analyses of these N1 NA proteins showed that the NA of the 2009 pandemic H1N1 strain shared at least 22 more amino acids in the head domain with the NAs of the avian H5N1 strains than with the NAs of seasonal human H1N1 viruses. Our data demonstrated LAIV-induced NA antibody responses in ferrets and cross-reactive NA antibodies induced by 2009 pandemic H1N1 and H5N1 LAIV viruses.     

中国2002～2003年度流行性感冒监测分析

目的 阐明2002年4月至2003年6月国内流行性感冒(流感)流行特点和流感病毒优势株的特性。方法 流感病毒分离采用鸡胚和细胞分离；流感病毒亚型鉴定采用血球凝集抑制试验；对流行株的HA基因核酸测序，分析其亲缘关系和抗原变异性。结果 2002年4月至2003年6月，全国23个省(市)和自治区共采集流感样患者咽拭子标本共计16135份，经鉴定流感病毒阳性1113株，分离率6．9％。在1113株流感病毒中，A1型66株、A3型544株、B型流感病毒Yamagada98株和Victoria405株，分别占总分离数的5．9％、48．9％、8．8％和36．4％。优势流行株为H3N2和B型Victoria株。A3型流感病毒除主要分离于2002年12月和2003年1月外，在非流行高峰期也有一定数量的分离。而B型Victoria系流感病毒主要集中分离于冬季流行高峰期，其流行株核酸序列分析属B型Victoria系株。A3型毒株血凝素基因的HA1系统树分析表明，其与A／Panama／2007／99同源，且有某些变异存在。结论 虽然感染人群的流感毒株依然是A1、A3和B型交叉出现，但以A型(H3N2)和B型Victoria为优势株。与历年不同，B型Victoria分离比例增加及分布广泛是2002～2003年度的特点。A型(H3N2)流行株有变异迹象值得密切注意。     

Serological studies of influenza viruses in pigs in Great Britain 1991-2.

Samples from a sow serum bank representative of the pig population of Great Britain collected during 1991-2, were examined for antibodies to influenza A, B and C viruses, using viruses which had been isolated from a variety of hosts. For influenza A viruses there was evidence of the continued circulation of classical swine H1N1 virus (26%) seroprevalence), and human H3N2 viruses (39%) which are antigenically most closely-related to A/Port Chalmers/1/73 virus. In addition antibodies were detected to A/swine/England/201635/92 (8%), a strain of H3N2 virus which appears to have arisen by antigenic drift from conventional H3N2 swine strains. Specific antibodies (2%) were detected to an H1N1 virus (A/swine/England/195852/92) related most closely to avian H1N1 strains. In tests with human H1N1 and H3N2 viruses, excluding isolates from pigs, the highest seroprevalence was detected to the prevailing strains from the human population. Serological tests with avian H4 and H10, human H2, equine 1 and 2 influenza A viruses were all negative. Seven pigs seropositive by haemagglutination-inhibition, virus neutralization and immunoblotting assays for antibody to influenza B virus, were randomly distributed geographically suggesting that influenza B viruses may be transmitted to pigs but fail to spread. The seroprevalence to influenza C viruses was 9.9% indicating that these viruses are widespread in pigs. These results provide further evidence that the pig can be infected by a number of influenza viruses, some of which may have significance in the epidemiology of human influenza.     

广东省流行性感冒病原学监测结果分析

目的分析广东省流行性感冒(流感)流行特点和流感病毒优势株的情况。方法采集2001年1月～2004年6月内科或儿科门诊就诊的流感样病人(发病3d内)的咽拭子或咽漱液标本，流感病毒分离采用鸡胚和狗肾传代细胞(Madin-Darby CanineKidney，MDcK)；流感病毒亚型鉴定采用血凝抑制试验。结果共采集流感样病例咽拭子或咽漱液样本17313份，流感病毒阳性1508株，分离率为8．71％，其中A1型(HIN1)92株、A3型(H3N2)1138株、B型278株，分别占总分离数的6．1％，75．5％，18．4％。3种毒株在5～15岁组分布最多，占44．7％；2001年优势流行株为B型，2002～2004年优势流行株均为A3(H3N2)；流感病毒分离高峰为每年3～7月，2003年和2004年上半年未分离到A1(H1N1)亚型流感病毒；A3(H3N2)型流感病毒除主要在流行季节分离外，在非流行高峰期也均有一定数量分离；B型流感病毒则主要集中分离于冬季(11、12、1月份)。结论感染人群中流感毒株A1(H1N1)、A3(H3N2)、B型交替出现，A3(H3N2)亚型活动较强。应密切注意A3型(H3N2)流行株的活动情况，加强监测，及时发现流感病毒新变异株。     

铜川市2013-2015年A型流感病毒HA基因特性研究

目的 应用生物信息学数据库和工具,了解2013-2014年铜川市A型H1N1和2013-2015年A型H3N2流感病毒血凝素(HA)基因特性及其抗原变异情况。 方法 收集铜川市哨点医院流感样病例标本,采用MDCK细胞分离流感病毒。用RT-PCR对部分A型H1N1、H3N2流感病毒进行HA基因序列扩增和纯化,序列测定,并用MEGA软件构建种系发生树分析。 结果 2013-2015年铜川市流感核酸检测标本共2 333份,流感阳性476份,阳性率20.40%。4株A型H1N1亚型流感病毒与WHO推荐A/California/07/2009(H1N1)疫苗株氨基酸序列比对,共发生11次氨基酸突变,其中3个氨基酸位点突变发生在抗原决定簇。3株A型H3N2亚型与WHO推荐的北半球2013-2014年A/Victoria/361/2011(H3N2)疫苗株比对共有9个氨基酸位点发生了突变,其中3个氨基酸位点发生在抗原决定簇;与WHO推荐的北半球2014-2015年A/Texas/50/2012(H3N2)疫苗株比对共有10个氨基酸位点发生了突变,有5个氨基酸位点发生在抗原决定簇。 结论 2013-2015年铜川市流行的A型H1N1、H3N2亚型流感病毒氨基酸发生突变导致抗原漂移。     

Antigenic and molecular heterogeneity in recent swine influenza A(H1N1) virus isolates with possible implications for vaccination policy

In order to explore the occurrence of antigenic drift in swine influenza A(H1N1) viruses and the match between epidemic and vaccine strains, 26 virus isolates from outbreaks of respiratory disease among finishing pigs in the Netherlands in the 1995/1996 season and reference strains from earlier outbreaks were examined using serological and molecular methods. In contrast to swine H3N2 viruses, no significant antigenic drift was observed in swine H1N1 viruses isolated from the late 1980s up to 1996 inclusive. However, a marked antigenic and genetic heterogeneity in haemagglutination inhibition tests and nucleotide sequence analyses was detected among the 26 recent swine H1N1 virus strains. Interestingly, the observed antigenic and molecular variants were not randomly distributed over the farms. This finding indicates independent introductions of different swine H1N1 virus variants at the various farms of the study and points to a marked difference between the epidemiologies of human and swine influenza viruses. The observed heterogeneity may hamper the control of swine influenza by vaccination and indicates that the efficacy of current swine influenza vaccines requires re-evaluation and that the antigenic reactivity of swine influenza viruses should be monitored on a regular basis.     

Influenza season 1999/2000 and vaccine composition for the season 2000/01

The first signs of influenza activity in the Netherlands during the 1999/2000 influenza season were the isolation of an influenza A (H3N2) virus in week 40 and of two more in week 43 of 1999. From week 50 onwards, a strong increase of the clinical influenza activity was observed which reached its peak in weeks 1 and 2 of 2000 and then rapidly declined. The clinical influenza activity was associated with the isolation of predominantly influenza A (H3N2) viruses. Near the end of the epidemic, influenza A (H1N1) and influenza B viruses were isolated sporadically. The antigenic properties of the influenza A (H3N2) viruses resembled those of the epidemic strains isolated in the previous season and the vaccine strain A/Sydney/5/97. This influenza season, influenza B viruses did not play a significant role and they matched the vaccine strain B/Yamanashi/166/98. In addition, a small number of influenza A (H1N1) viruses were isolated. Some of these viruses resembled the old variant of influenza A (H1N1) viruses, A/Bayern/7/95, whilst others showed a close antigenic relationship with the vaccine strain recommended for the next influenza season, A/New Caledonia/20/99. For the influenza season 2000/'01, it is recommended by the World Health Organization that the vaccines contain the following (or similar) virus strains: A/Moscow/10/99 (H3N2), A/New Caledonia/20/99 (H1N1) and B/Beijing/184/93.     

浙江省与日本A3型流行性感冒病毒株的血凝特性及HA1序列比较

目的：比较近年来在浙江省与日本流行的A3（H3N2）型流流行性感冒（流感）毒株的血凝特征与血凝素重链（HA1）区域的序列差异,方法：对浙江省不同性状的流感代表进行了抗原性分析,并与日本同期毒株作了血凝特性及HA1区域的氨基酸序列比较分析,结果：近年在浙江流行的A3型流行株,其抗原性已发生较大变异,其中绝大部分是对鸡红细胞缺乏凝集特性的O相毒株,它与A／武汉／359／95株二者在HA1区域的氨基酸同源性仅为94．82％,存在较大差异,这些O相毒株可以通过在MDCK细胞上的传代而转变为D相毒株,日本的同期毒株,其情况也相似,结论：A3型流感病毒在HA1区域发生的变异,是近年来引起浙江省流感流行的主要因素。     

2003年广州市流行性感冒病原学及血清学监测分析

目的　分析、掌握广州市流感病原学变化特点及流行趋势。方法　病例标本来自广州市 3家哨点医院的流感样病例和局部暴发疫点现患病例的漱口液或咽拭子 ;普通人群血清标本于流感流行高峰前 (3月 )和高峰后 (9月 )在其中一家哨点医院按 0～、5～、15～、2 5～、6 0岁以上 5个年龄组分层随机抽取普通人群进行采集 ;职业暴露人群血清标本于 9月份在花都区、从化市、增城市抽取饲养、销售、屠宰家禽职业人员进行采集。病原学采用MDCK细胞进行病毒分离 ,血清学采用微量半加敏红细胞抑制试验检测各型流感抗体。结果　检测 192 5份流感样病例标本 ,分离出流感病毒 2 6 5株 ,其中H3N2亚型 2 5 6株 ,B型 9株 ,分别占总病毒株的 96 6 %和 3 4 % ,未分离出H1N1亚型毒株 ;4～ 7月份分离的H3N2亚型毒株共 2 2 8株 ,占全年的 86 0 % ,此期未分离出B型毒株。全年共报告流感样局部暴发疫情 91起 ,4～ 7月份流行高峰期报告 82起 ,占全年的 90 1% ,其中 5 6起 (占 6 8 3% )为H3N2亚型引起。 3、9月份分别采集普通人群血清标本 180和 15 0份 ,流感病毒各型抗体中H3N2亚型抗体阳性率最高 ,3月份为 85 6 % (15 4 / 180 ) ,9月份为 90 7% (136 / 15 0 ) ;H1N1亚型、B(维多利亚系 ) 和B(巴拿马系 ) 抗体阳性率偏低 ,仅为 8     

天津市儿童流行性感冒病原学检测分析

目的：对天津市2001－2002年流行性感冒（流感）患儿进行病原学分析。方法：用狗肾传代（MDCK）细胞和鸡胚双腔法进行流感病毒分离。用鸡红细胞和人O型红细胞凝集试验证实病毒的存在,用红细胞凝集抑制试验进行型和亚型的鉴定。结果：2001年10月至2002年3月共采集14岁以下流感样患儿咽拭子标本238份,发离出64株流感病毒,检出率为26．9％;其中A（H3N2）亚型42株,占检出数的65．6％;A（H1N1）亚型13株,占20．3％;B型9株,占14．1％,所分离的64株流感病毒都具有适应于MDCK细胞株生长及与人O型红细胞凝集良好的生物学特性,转种鸡胚后,绝大多数（62／64）能适应鸡胚生长;但64份阳性咽拭子标本液直接接种鸡胚,仅有3份血凝阳性,此外,96．4％（53／55株）A型流感病毒均可由O相转为D相,有2株A（H3N2）为O相特征,B型流感病毒均为O相特征,结论：天津地区流感病毒存在A（H3N2）、A（H1A1）和B三个型,以A（H3N2）为优势流行型。     

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.     

Surveillance of influenza viruses isolated from travellers at Nagoya International Airport

In order to conduct a survey of influenza viruses entering Japan via travellers arriving by airplanes, gargle solutions were collected from passengers who reported to the quarantine station of Nagoya International Airport complaining of respiratory symptoms. From 504 samples collected between August 1996 and March 1999, 30 influenza virus strains were isolated. Twenty-eight of the isolates were influenza A (H3N2) viruses and two were influenza B viruses. No H1N1 virus was isolated. Among 28 isolates of H3N2 virus, 3 strains were obtained outside the influenza season. Nucleotide sequences of the haemagglutinin (HA) genes of these isolates along with those from domestic patients were analysed in order to determine the influence of imported influenza viruses by travellers on epidemics in Japan. From the phylogenetic and chronological aspects, the possibility was suggested in one case in 1997/8 and two in the 1998/9 season that imported virus by travellers may have influenced the domestic influenza epidemics.     

2007-2008年吉林省H3N2亚型流感病毒HA1基因序列分析

目的了解2007-2008年间吉林省H3N2亚型流感病毒HA1基因的演变特征。方法采用MD-CK细胞分离培养流感病毒,提取病毒RNA,经逆转录和聚合酶链式反应扩增后测序。结果①2007-2008年吉林省流行的H3N2亚型流感毒株核苷酸同源性为98.9%～100%,与同期WHO推荐的疫苗株A/Wisconsin/67/05相比有10～14个氨基酸位点发生变化,并且在122位增加了一个糖基化位点;②长春市11月与12月分离的病毒株在进化树上处于不同的两个侧枝;③在同一流行高峰吉林省8个市州分离的流感病毒株在进化树上形成不同的两簇。结论2007-2008年吉林省流行的H3N2亚型流感毒株与WHO推荐的疫苗株A/Wisconsin/67/05相比已经发生一定变化;不同时间及市州流行的病毒株也有差异。     

2012-2018年青岛市A型(H1N1)pdm09流感病毒奥司他韦耐药株基因特征

目的 了解2012-2018年青岛市人群A型(H1N1)pdm09流感病毒奥司他韦耐药株基因特征。方法 收集2012年4月-2018年3月间青岛市A(H1N1)pdm09毒株397份,逆转录聚合酶链反应(RT-PCR)扩增神经氨酸酶(Neuraminidase,NA)和血凝素(Hemagglutinin,HA)基因全长,序列测定后进行耐药位点和氨基酸变异及进化分析。结果 5株发生了H275Y突变,为奥司他韦耐药株;另有4株S247N突变,可能为奥司他韦耐药株。2012-2018年H275Y突变株检出率依次为2.8 %、2.0 %、0.0 %、1.1 %、0.0 %和0.7 %。NA和HA进化树显示,2012-2013年青岛H275Y突变株与美国耐药株A/Tennessee/03/2013更接近,2013-2014年青岛H275Y突变株与国内株和日本札幌耐药株更接近,这两个年度耐药株的毒株起源可能有所不同。突变株在酶活性位点、抗原决定簇、受体结合位点及其他功能位点(如HA位点D222、Q223和NA位点V241I、N369K和N386K)的转变与野生敏感株一致。结论 青岛市A型(H1N1)pdm09流感病毒奥司他韦耐药株明显增加且流行起源不同,但并未取得比野生株更强的流行能力。奥司他韦仍可作为流感预防和治疗的有效手段。     

Characterization of high-growth reassortant influenza A viruses generated in MDCK cells cultured in serum-free medium

In the present study reassortant influenza A viruses of both the H1N1 and H3N2 type were generated in Madin Darby Canine Kidney cells grown in the absence of fetal bovine serum (MDCK-SF1 cells). To this end, MDCK-SF1 cells were simultaneously infected with one of the high-growth laboratory strains A/Puerto Rico/8/34 (H1N1) or A/Hong Kong/2/68 (H3N2) and recent H3N2 and H1N1 vaccine strains, respectively. Reassortant viruses obtained from these mixed infections were genetically characterized by RT-PCR and restriction enzyme analysis and their growth properties were compared to those of the corresponding field strains. Reassortant H3N2 viruses inherited the matrix and polymerase pa gene whilst H1N1 reassortant viruses inherited the matrix and polymerase pbl gene of the high-growth parent. Reassortant viruses generally gave higher viral yields, as measured by a haemagglutination assay, than their wild type counterparts. The procedure followed results in the generation of high-growth reassortant viruses in weeks. The use of MDCK-SF1 cells together with these reassortants for generating influenza virus antigens can significantly speed up the vaccine production procedure.