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.     

The 2006/'07 influenza season in the Netherlands and the vaccine composition for the 2007/'08 season

The influenza epidemic of 2006/'07 began late in the season, like the two previous influenza epidemics. In week 8 a peak of modest height was reached. As usual, the causal strains were mainly A/H3N2 viruses and to a lesser extent A/H1N1 and B viruses. A new A/H1N1 virus variant has emerged, an event that on average takes place only every 10 years. However, almost all A/H1N1 virus isolates belonged to the old variant and were similar to the vaccine virus. The A/H3N2 virus isolates appeared to deviate from the vaccine strain, but after antigenic cartographic analysis and correction for low avidity they proved also closely related to the vaccine strain. The few type B virus isolates belonged to the B/Yamagata/16/88 lineage, whereas the used B vaccine virus had been chosen from the B/Victoria/2/87 lineage. The vaccine therefore will have provided almost optimal protection against the circulating influenza A/H1N1 and A/H3N2 viruses but not against the influenza B viruses. For the 2007/'08 influenza season the World Health Organization has recommended the following vaccine composition: A/Solomon Islands/3/06 (H1N1) (new), A/Wisconsin/67/05 (H3N2), and B/Malaysia/2506/04.     

Genetic relationship between the HA genes of type A influenza viruses isolated in off-seasons and later epidemic seasons

From January 1985 to March 1989, off-season viruses of H1N1 and H3N2 subtypes of influenza A viruses were isolated on five occasions in Japan. The HA gene sequences of the influenza A(H1N1) and A(H3N2) viruses isolated in Japan from 1985-9 were analysed and the phylogenetic tree for each subtype virus was constructed to determine any genetic relationship between viruses isolated in off-seasons and the epidemic viruses of the following influenza seasons. In one instance with H1N1 viruses in 1986 and in two instances with H3N2 viruses in 1985 and 1987, the spring isolates were genetically close to some of the winter isolates and were considered to be the parental viruses of the following influenza seasons. However, even in these cases, influenza viruses of the same subtype with different lineages co-circulated in Japan.     

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.     

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。     

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.     

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.     

安徽省2株人感染H9N2流感病毒基因特征

目的 分析2015年安徽省2株人感染H9N2禽流感病毒分离株全基因组特征。方法 对安徽省2015年4月和9月流感监测网络实验室先后发现并确诊的2例H9N2禽流感病毒感染病例及其病毒分离株全基因组序列进行分析,使用Mega 6.0等软件解析2株H9N2毒株全基因组特征。结果 安徽省首次报道人感染H9N2禽流感病毒病例,对病毒分离株分析显示,其HA和NA基因与中国2013年禽间流行的H9N2病毒高度同源,属于A/Chicken/Shanghai/F/98(H9N2)支系;而PB2和MP基因属于A/quail/Hong Kong/G1/97支系,与H7N9、H10N8和H6N2具有较高的相似度。氨基酸序列比对发现该2株病毒出现多个人易感倾向位点分子特征:HA蛋白发生Q226L、H183N和E190T突变,且HA裂解位点为PSRSSR\GL排列,NA蛋白茎部发生63~65位氨基酸缺失,M2蛋白S31N突变,以及PA-100A、PA-356R和PA-409N。结论 安徽省首次报道的人感染禽源H9N2流感病毒为H9N2系间重配病毒,存在多个人易感位点。     

Annual report of the National Influenza Surveillance Scheme, 2000.

Surveillance of influenza in Australia in 2000 was based on data from national and state-based sentinel general practice consultations for influenza-like illness, laboratory isolations of influenza virus and absenteeism rates from a national employer. The peak in influenza cases was in mid-September. Influenza A was the dominant strain, with the highest proportion being influenza A (H3N2), but with a significant proportion of isolates of influenza A (H1N1) (16%) for the first time since 1995. The influenza A (H3N2) isolates were predominantly related to A/Moscow/10/99 and vaccine strain A/Panama/2007/99. Influenza A (H1N1) was predominantly A/New Caledonia/20/99. The proportion of Influenza B viruses isolated also increased in keeping with a three-yearly cycle of influenza B epidemics in Australia. influenza B isolates showed a progressive drift away from the B/Beijing/184/93 strain with the majority closely related to the B/Sichuan/379/99 strain. In 2000, influenza vaccination levels reached 74 per cent in persons aged over 65 years.     

广州市甲型H1N1流感病毒的持续进化变异监测

目的 通过对H1N1流感病毒进行基因进化变异监测,为H1N1流感的科学防控提供研究数据.方法 对广州市2017-2019年132株H1N1流感病毒进行血凝素(Hemagglutinin,HA)和神经氨酸酶(Neuraminidase,NA)基因测序,分析不同流行年度病毒的分子变异特点.结果2017-2019年广州市H1...     

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.     

2015-2017年盐城市甲型H3N2流感病毒HA1、NA基因分子特征

目的 从分子流行病学角度对盐城市2015-2017年流行的甲型H3N2流感病毒血凝素（hemagglutinin,HA）和神经氨酸酶（neuraminidase,NA）基因的分子特征进行研究。方法 收集盐城市2015-2017年流感监测哨点医院以及流感爆发点采集的3 891例流感样病例标本进行核酸检测和病毒分离,从中筛选出20株经血凝抑制试验（hemagglutination inhibition,HI）验证为甲型H3N2亚型的毒株,采用反转录聚合酶链式反应方法扩增其HA1和NA基因并进行测序。结果 2015-2017年流行的20株甲型H3N2毒株HA1和NA基因各自分支的聚类关系基本一致。盐城市A/Jiangsu-YC/1474/2015、A/Jiangsu-YC/1725/2015两株分离株与疫苗株A/Switzerland/9715293/2013和A/Hongkong/4801/2014的进化距离较近,而其余18株分离株与国内部分省市相近年份毒株亲缘关系相近,并与疫苗株A/Switzerland/9715293/2013和A/Hongkong/4801/2014进化距离较远。该20株毒株HA1基因编码区抗原表位、受体结合位点和糖基化位点均发生了一定程度变异。从基因变异角度进行分析,疫苗株A/Switzerland/9715293/2013对盐城地区流感流行的保护效果要弱于疫苗株A/Hongkong/4801/2014。结论 2015-2017年盐城市流行的甲型H3N2毒株HA1和NA基因已逐渐发生变异,可能导致流感病毒发生实质性的抗原性漂移,降低与流感疫苗株的匹配度,减弱流感疫苗的保护作用。     

Laboratory-based surveillance of influenza virus in the United States during the winter of 1977--1978. II. Isolation of a mixture of A/Victoria- and A/USSR-like viruses from a single person during an epidemic in Wyoming, USA, January 1978

At a time when outbreaks and sporadic cases of influenza caused a A/Victoria/3/75-like and A/Texas/1/77-like H3N2 strain of influenza were occurring in the Rocky Mountain region of the USA, about 60% of the students of a high school in Cheyenne, Wyoming, were involved in an outbreak of influenza-like illness. Six influenza A(H1N1) virus isolates were obtained from throat swabs collected from 12 of these students. Virus isolated from a seventh student, however, contained a mixture of H1 and H3 (A/Victoria/3/75-like) hemagglutinins and N1 and N2 neuraminidases, as shown by the ability to clone from the mixture viruses with antigenic components H1N1, H3N1, and H3N2. An antigenic hybrid virus with H3N1 composition was re-isolated from the original throat swab. The results show that one student was shedding a mixture of A/Victoria/3/75(H3N2)-like and A/USSR/90/77(H1N1)-like viruses at the time his throat swab was taken.     

Concurrent antigenic analysis of recent epidemic influenza A and B viruses and quantitation of antibodies in population serosurveys in Italy

Laboratory investigations of virus isolation and serum antibodies in a Mediterranean country (Italy) demonstrated that influenza A and B viruses, and often both, circulated every winter in Italy.The winter 1987/88 was characterized by a low level of influenza activity, as shown by the limited number (47) of influenza virus isolates, the majority of which (61%) belonged to the influenza B type. In contrast, the 1988/89 influenza season was exclusively associated with the circulation of influenza type A viruses. The A(HlH1) subtype was largely predominant (97%), as compared to the low incidence of the A(H3N2) subtype (3%). During the 1989/90 winter a cocirculation of A and B influenza viruses was observed, A(H3N2) strains being responsible for 96% of the virologically confirmed cases.Antigenic analysis of the virus isolates showed some antigenic variation in influenza A viruses of both HlN1 and H3N2 subtypes, whilst antigenic stability was found among the influenza B virus isolates.Overall, the above virological findings correlate with the data concerning the pattern of influenza virus circulation in Northern Europe and the UK during the three years surveyed.The results of serum antibody surveys conducted in each post-epidemic period are also reported.     

Comparison of influenza viruses isolated from man and from whales.

Four isolates of influenza virus strains from Moscow and Habarovsk that caused outbreaks of influenza in November and December 1977 in several cities of the USSR were studied and their haemagglutinins and neuraminidases were compared with those of other human and animal influenza viruses including A/whale/Pacific Ocean/76. In H1 tests these isolates, designated A/USSR/77, reacted with immune serum against A/FM/1/47 (H1N1) to the homologous titre, and with antiserum against A/whale/PO/19/76 virus to 1/8 of the homologous titre. In neuraminidase inhibition tests all A/USSR/77 isolates showed the presence of human N1 type neuraminidase, more closely related to A/sw/New Jersey/76 (Hsw1N1) than to A/FM/1/47 (H1N1) virus. The haemagglutinin of A/whale/Pacific Ocean/19/76 virus occupies an intermediate position between H0 and H1, but its neuraminidase is close to Nav2. The virus from whales multiplies better at low (28°C) and at high (40°C) temperatures than do the viruses of human origin that were tested.     

Influenza A virus (H3N8) in dogs with respiratory disease, Florida

In 2004, canine influenza virus subtype H3N8 emerged in greyhounds in the United States. Subsequent serologic evidence indicated virus circulation in dog breeds other than greyhounds, but the virus had not been isolated from affected animals. In 2005, we conducted virologic investigation of 7 nongreyhound dogs that died from respiratory disease in Florida and isolated influenza subtype H3N8 virus. Antigenic and genetic analysis of A/canine/Jacksonville/2005 (H3N8) and A/canine/Miami/2005 (H3N8) found similarity to earlier isolates from greyhounds, which indicates that canine influenza viruses are not restricted to greyhounds. The hemagglutinin contained 5 conserved amino acid differences that distinguish canine from equine lineages. The antigenic homogeneity of the canine viruses suggests that measurable antigenic drift has not yet occurred. Continued surveillance and antigenic analyses should monitor possible emergence of antigenic variants of canine influenza virus.     

Swine-origin influenza A (H3N2) virus infection in two children--Indiana and Pennsylvania, July-August 2011

Influenza A viruses are endemic in many animal species, including humans, swine, and wild birds, and sporadic cases of transmission of influenza A viruses between humans and animals do occur, including human infections with avian-origin influenza A viruses (i.e., H5N1 and H7N7) and swine-origin influenza A viruses (i.e., H1N1, H1N2, and H3N2). Genetic analysis can distinguish animal origin influenza viruses from the seasonal human influenza viruses that circulate widely and cause annual epidemics. This report describes two cases of febrile respiratory illness caused by swine-origin influenza A (H3N2) viruses identified on August 19 and August 26, 2011, and the current investigations. No epidemiologic link between the two cases has been identified, and although investigations are ongoing, no additional confirmed human infections with this virus have been detected. These viruses are similar to eight other swine-origin influenza A (H3N2) viruses identified from previous human infections over the past 2 years, but are unique in that one of the eight gene segments (matrix [M] gene) is from the 2009 influenza A (H1N1) virus. The acquisition of the M gene in these two swine-origin influenza A (H3N2) viruses indicates that they are "reassortants" because they contain genes of the swine-origin influenza A (H3N2) virus circulating in North American pigs since 1998 and the 2009 influenza A (H1N1) virus that might have been transmitted to pigs from humans during the 2009 H1N1 pandemic. However, reassortments of the 2009 influenza A (H1N1) virus with other swine influenza A viruses have been reported previously in swine. Clinicians who suspect influenza virus infection in humans with recent exposure to swine should obtain a nasopharyngeal swab from the patient for timely diagnosis at a state public health laboratory and consider empiric neuraminidase inhibitor antiviral treatment to quickly limit potential human transmission.     

Systematic evaluation of suspension MDCK cells,adherent MDCK cells,and LLC-MK2 cells for preparing influenza vaccine seed virus

Suspension Madin–Darby canine kidney (MDCK) cells (MDCK-N), adherent MDCK cells (MDCK-C), and adherent rhesus monkey kidney LLC-MK2 cells (LLC-MK2D) were systematically evaluated for the preparation of influenza vaccine seed viruses for humans on the basis of primary virus isolation efficiency, growth ability, genetic stability of the hemagglutinin (HA) and neuraminidase (NA) genes, and antigenic properties in hemagglutination inhibition (HI) test of each virus isolate upon further passages. All the subtypes/lineages of influenza viruses (A(H1N1), A(H1N1)pdm09, A(H3N2), B-Victoria, and B-Yamagata) were successfully isolated from clinical specimens by using MDCK-N and MDCK-C, whereas LLC-MK2D did not support virus replication well. Serial passages of A(H1N1) viruses in MDCK-N and MDCK-C induced genetic mutations of HA that resulted in moderate antigenic changes in the HI test. All A(H1N1)pdm09 isolates from MDCK-C acquired amino acid substitutions at the site from K153 to N156 of the HA protein, which resulted in striking antigenic alteration. In contrast, only 30% of MDCK-N isolates showed amino acid changes at this site. The frequency of MDCK-N isolates with less than two-fold reduction in the HI titer was as high as 70%. A(H3N2) and B-Yamagata isolates showed high antigenic stability and no specific amino acid substitution during passages in MDCK-N and MDCK-C. B-Victoria isolates from MDCK-N and MDCK-C acquired genetic changes at HA glycosylation sites that greatly affected their antigenicity. When these cell isolates were applied to passages in hen eggs, A(H1N1), B-Victoria, and B-Yamagata viruses grew well in eggs, while none of the cell isolates of A(H3N2) viruses did. Thus, we demonstrate that MDCK-N might be useful for the preparation of influenza vaccine seed viruses.     

Human infections with novel reassortant influenza A(H3N2)v viruses, United States, 2011

During July-December 2011, a variant virus, influenza A(H3N2)v, caused 12 human cases of influenza. The virus contained genes originating from swine, avian, and human viruses, including the M gene from influenza A(H1N1)pdm09 virus. Influenza A(H3N2)v viruses were antigenically distinct from seasonal influenza viruses and similar to proposed vaccine virus A/Minnesota/11/2010.     

The 2002/2003 influenza season in the Netherlands and the vaccine composition for the 2003/2004 season

As in the 2000/2001 and 2001/2002 seasons, the influenza epidemic in the 2002/2003 season started late (week 7 of 2003) and was only moderate in size. Influenza A (H3N2) and B viruses were detected in equal numbers among patients of general practitioners and these two viruses were therefore equally responsible for the epidemic. However, H3N2 viruses dominated isolates taken from hospitals. In haemagglutination-inhibition (HI) assays most of the H3N2 viruses proved highly reactive with antiserum to the vaccine-reference strain A/Moscow/10/99. This was also true for a number of isolates, including those obtained from nursing home residents, closely related to the reference strain A/Finland/170/03. However, an estimated 4% of the H3N2 isolates belonged to the variant A/Fujian/411/02 from China, which constituted the majority of the H3N2 viruses isolated in Europe in the later phase of the season. This variant reacted poorly with antiserum to A/Moscow/10/99. In H1 tests all influenza A(H1N1)-virus isolates and all B-virus isolates were closelyrelated to the corresponding vaccine-reference strains. Taking this data into consideration, the World Health Organization has advised the same vaccine composition for the 2003/2004 season as for the 2002/2003 season, namely: A/Moscow/10/99 (H3N2), A/New Caledonia/20/99 (H1N1) and B/Hong Kong/330/01. There is the possibility of a mismatch occurring between the H3N2-vaccine strain and the circulating H3N2 viruses in the coming influenza season. In March and April 2003 there was an outbreak of influenza-A (H7N7) fowl plague in the Netherlands. A special monitoring survey revealed that 91 people who had handled infected poultry became infected with the H7N7 virus. One of these later died as a result of this. None of the avian and human H7N7-virus isolates examined contained human or porcine influenza-A virus genes.