Isolation of novel triple-reassortant swine H3N2 influenza viruses possessing the hemagglutinin and neuraminidase genes of a seasonal influenza virus in Vietnam in 2010

Surveillance of swine influenza viruses (SIVs) in 31 pig farms in northern and southern parts of Vietnam was conducted. Six H3N2 influenza A viruses were isolated from a pig farm in southern Vietnam. They were novel genetic reassortants between a triple-reassortant SIV and a human seasonal H3N2 virus. Their hemagglutinin and neuraminidase genes were derived from a human virus circulating around 2004-2006 and the remaining genes from a triple-reassortant SIV that originated in North America. This is the first report describing the isolation of a novel triple-reassortant SIV in Vietnam.     

Inference of age-dependent case-fatality ratios for seasonal influenza virus subtypes A(H3N2) and A(H1N1)pdm09 and B lineages using data from the Netherlands

Background

Despite the known relatively high disease burden of influenza, data are lacking regarding a critical epidemiological indicator, the case-fatality ratio. Our objective was to infer age-group and influenza (sub)type specific values by combining modelled estimates of symptomatic incidence and influenza-attributable mortality.

Methods

The setting was the Netherlands, 2011/2012 through 2019/2020 seasons. Sentinel surveillance data from general practitioners and laboratory testing were synthesised to supply age-group specific estimates of incidence of symptomatic infection, and ecological additive modelling was used to estimate influenza-attributable deaths. These were combined in an Bayesian inferential framework to estimate case-fatality ratios for influenza A(H3N2), A(H1N1)pdm09 and influenza B, per 5-year age-group.

Results

Case-fatality estimates were highest for influenza A(H3N2) followed by influenza B and then A(H1N1)pdm09 and were highest for the 85+ years age-group, at 4.76% (95% credible interval [CrI]: 4.52–5.01%) for A(H3N2), followed by influenza B at 4.08% (95% CrI: 3.77–4.39%) and A(H1N1)pdm09 at 2.51% (95% CrI: 2.09–2.94%). For 55–59 through 85+ years, the case-fatality risk was estimated to double with every 3.7 years of age.

Conclusions

These estimated case-fatality ratios, per influenza sub(type) and per age-group, constitute valuable information for public health decision-making, for assessing the retrospective and prospective value of preventative interventions such as vaccination and for health economic evaluations.     

2014-2015年商洛市流感病毒H3N2亚型血凝素(HA1)基因进化研究

目的分析2014-2015年度商洛市流感监测病毒血凝素(HA)基因变异情况并研究与推荐疫苗的匹配性。方法收集2014-2015年商洛市流感监测平台用狗肾传代细胞(MDCK)培养分离的H3N2亚型毒株,利用RT-PCR方法扩增分离HA片段,进行核苷酸序列测定,应用clustax2.1软件进行序列比对后,用Mega6.0软件构建系统发育进化树,系统进化树采用Neighboring-joining方法进行分析。结果 2014-2015年度分离的流感H3N2毒株同源性在97.2%~99.9%,与推荐疫苗株A/Texas/50/2012同源性为97.3%~98.5%;将分离毒株的HA1基因氨基酸与疫苗株比较,发现2014年毒株主要抗原决定簇氨基酸变异点有B区Y159F、S198P;2015年主要抗原决定簇氨基酸变异点有A区G142R,B区S159F、S198P。结论2014-2015年度商洛市流感H3N2亚型毒株关键抗原决定簇已经出现改变,A/Texas/50/2012作为疫苗组分已经不是最佳,亟需对我国流感H3N2亚型疫苗组分进行更新,应密切关注流感H3N2基因进化趋势。     

Triple‐reassortant influenza A virus with H3 of human seasonal origin,NA of swine origin,and internal A(H1N1) pandemic 2009 genes is established in Danish pigs

This report describes a triple‐reassortant influenza A virus with a HA that resembles H3 of human seasonal influenza from 2004 to 2005, N2 from influenza A virus already established in swine, and the internal gene cassette from A(H1N1)pdm09 has spread in Danish pig herds. The virus has been detected in several Danish pig herds during the last 2‐3 years and may possess a challenge for human as well as animal health.     

禽流感病毒H1、H3、H5、N2亚型多重RT-PCR检测方法的初步研究

目的根据禽流感病毒H1、H3、H5亚型的HA基因和N2型NA基因的保守序列,设计出四对RT-PCR引物,建立一步法多重RT-PCR对禽流感H1、H3、H5、N2四亚型进行快速检测。方法利用所设计的四对引物,通过对该方法扩增条件的优化,成功建立快速检测禽流感病毒H1、H3、H5、N2四亚型的一步法多重RT-PCR。利用禽流感H1、H3、H5、N2四亚型毒株和其它相关标准毒株进行敏感性和特异性试验。结果与结论所建立的一步法多重RT-PCR具有较高的特异性和敏感性,与禽流感其它亚型和NDV、IBV、ARV?IBDV的核酸均无交叉反应。用该方法检测现场样品395份(4省20多个地区),结果与经典检测方法一致。     

Human infection with avian influenza A(H7N2) virus—Virginia, 2002

Background

In March 2002, an outbreak of low‐pathogenic avian influenza (LPAI) A(H7N2) was detected among commercial poultry operations in Virginia.

Methods

We performed a serosurvey of 80 government workers involved in efforts to control the outbreak.

Results

One study participant who assisted with disposal of infected birds tested positive for neutralizing antibodies to influenza A(H7N2) by microneutralization assay and H7‐specific IgM antibodies by enzyme‐linked immunosorbent assay (ELISA). The acute infection was temporally associated with an influenza‐like illness that resolved without hospitalization.

Conclusion

This study documents the earliest evidence of human infection with an H7 influenza virus of the North American lineage.     

儿童甲型H1N1流感63例临床观察

目的 探讨儿童甲型H1N1流感的流行特征、临床特点及实验室指标.方法　对我院收治的63例儿童甲型H1N1流感的流行病学史、临床表现、实验室指标、治疗及转归进行回顾性总结分析.结果　多数患儿有流感患者接触史,症状以发热(高热为主)、咳嗽及咽痛为主.实验窜检查:全部患儿ALT、肾功能及血钾均正常,部分患儿CK、LDH及α-...     

2010--2012年福建省H3N2亚型流感病毒血凝素基因特征分析

目的通过对2010—2012年福建省分离的H3N2亚型流感毒株血凝素HA1基因进行分析,了解2010-2012年福建省H3N2亚型流感病毒的基因特征和变异规律。方法随机选择28株毒株,提取病毒RNA,采用RT-PCR扩增目的片段,纯化PCR产物后进行测序;利用DNAstar和Mega4．0等生物信患学软件进行核苷酸整理、拼接、校对、差异性比较以及基因进化树构建等分析研究。结果28株H3N2亚型流感病毒HAl区核苷酸同源性在96．4％～100％之间。基因系统进化分析显示,其进化规律都是沿着树枝主干随着时闻推移向,上延伸,序列的差异和年代成正比。2010—2012年间HAl区共出现43个氨基酸位点的变化,其中有10个氨基酸位点变异累计涉及4个抗原决定簇,2个变异位点发生在受体结合位点（RBS）及其附近,应予高度重视。结论相对于A／Perth／16／2009疫苗代表株,2012年的部分H3N2亚型流感出现了抗原漂移;部分毒株已出现氨基酸位点的改变,并涉及抗原决定簇及受体结合位点,提示2010—2012年福建省人群中流行的H3N2亚型流感正逐渐发生变异,应加强流感病原学监测,以及时发现新的流感变异株,为福建省流感防控提供科学依据。     

2017—2019年贵州省H3N2亚型流感病毒流行特征及NA基因遗传特性分析

目的 分析2017—2019年贵州省H3N2亚型流感病毒流行特征及神经氨酸酶(Neuramini dase,NA)基因的遗传特性,为H3N2亚型流感病毒的防控提供科学依据。方法 采集2017—2019年贵州省13家国家级流感监测哨点医院的流感样病例(ILI)咽拭子标本,进行荧光定量PCR的检测,以自然年度为监测周期进行统计分析。H3N2亚型核酸阳性的标本进行狗肾胚细胞(MDCK)分离病毒,收集培养液提取病毒RNA,进行RT-PCR特异性NA基因扩增,扩增产物纯化后进行测序,用MAGE7.0软件和Clustal W2软件进行同源性、遗传进化和耐药位点分析。结果 2017-2019年,贵州省采集ILI咽拭子标本分别为15 553、15 164和15 348份,H3N2亚型阳性率分别为5.12%(797/15 553)、0.80%(122/15 164)和7.67%(1 177/15 348),呈交替流行趋势;高峰期主要出现在1-3月和10-12月。2017-2019年H3N2亚型NA基因核苷酸同源性为97.5%~100%,在进化树上主要分成2个分支,所有毒株NA基因关键位点均未发生突变。结论 贵州省H3N2亚型流感病毒呈年度周期性流行,多发于冬春季节,为更好防控流感,应及时掌握流行趋势,需加强监测并及时分析病毒基因特征变异情况。     

Analytical detection of influenza A(H3N2)v and other A variant viruses from the USA by rapid influenza diagnostic tests

Please cite this paper as: Balish et al. (2012) Analytical detection of influenza A(H3N2)v and other A variant viruses from the USA by rapid influenza diagnostic tests. Influenza and Other Respiratory Viruses 7(4), 491–496. Background The performance of rapid influenza diagnostic tests (RIDTs) that detect influenza viral nucleoprotein (NP) antigen has been reported to be variable. Recent human infections with variant influenza A viruses that are circulating in pigs prompted the investigation of the analytical reactivity of RIDTs with these variant viruses. Objectives To determine analytical reactivity of seven FDA‐cleared RIDTs with influenza A variant viruses in comparison with the reactivity with recently circulating seasonal influenza A viruses. Methods Tenfold serial dilutions of cell culture–grown seasonal and variant influenza A viruses were prepared and tested in duplicate with seven RIDTs. Results All RIDTs evaluated in this study detected the seasonal influenza A(H3N2) virus, although detection limits varied among assays. All but one examined RIDT identified the influenza A(H1N1)pdm09 virus. However, only four of seven RIDTs detected all influenza A(H3N2)v, A(H1N2)v, and A(H1N1)v viruses. Reduced sensitivity of RIDTs to variant influenza viruses may be due to amino acid differences between the NP proteins of seasonal viruses and the NP proteins from viruses circulating in pigs. Conclusions Clinicians should be aware of the limitations of RIDTs to detect influenza A variant viruses. Specimens from patients with influenza‐like illness in whom H3N2v is suspected should be sent to public health laboratories for additional diagnostic testing.     

The avian‐origin H3N2 canine influenza virus that recently emerged in the United States has limited replication in swine

Equine‐origin H3N8 has circulated in dogs in the United States since 1999. A genetically and antigenically distinct avian‐origin H3N2 canine influenza was detected in March of 2015 in Chicago, Illinois. Subsequent outbreaks were reported with over 1000 dogs in the Midwest affected followed by 23 additional states with detections within 5 months. The potential for canine‐to‐swine transmission was unknown. Experimental infection in pigs showed this virus does not replicate efficiently in swine.     

Analysis of the acute‐phase protein response in pigs to clinical and subclinical infection with H3N2 swine influenza virus

Background

Swine influenza (SI) is a contagious, important respiratory disease. Diagnosis of SI is based on the clinical signs, confirmed by the detection of viral RNA or specific antibodies. However, the infection is much more frequent than the disease.

Objectives

The aim of study was to investigate the kinetics of acute-phase protein (APP) response during subclinical and clinical influenza in pigs. The utility of APP measurements in identification of infected animals was also evaluated.

Methods

Twenty-eight piglets were used. C-reactive protein (CRP), haptoglobin (Hp), serum amyloid A (SAA) and pig major acute-phase protein (Pig-MAP) concentrations in serum were measured using commercial ELISAs.

Results and Conclusions

No relevant clinical signs were observed in intranasally infected pigs. In contrast, coughing, nasal discharge, and fever were observed in pigs infected intratracheally. All infected pigs exhibited specific antibodies in the serum at 10 dpi, and viral shedding was confirmed. The concentrations of CRP, Hp and SAA were significantly increased after infection. The level of Pig-MAP remained constant during subclinical and clinical infection. The concentrations of CRP, Hp and SAA were higher in pigs with clinical disease. Although not specific, strategic APP measurements may reveal ongoing clinical and subclinical infection. A close relationship between the magnitude of serum APP response with the severity of disease, providing an objective tool for validation the severity of infection. The maximum concentration of SAA in serum was closely correlated with lung score and makes this APP potential indicator for disease progress or estimation of treatment strategy.     

An open‐label phase I trial of a live attenuated H2N2 influenza virus vaccine in healthy adults

Please cite this paper as: Talaat et al. (2012) An open‐label phase I trial of a live attenuated H2N2 influenza virus vaccine in healthy adults. Influenza and Other Respiratory Viruses DOI: 10.1111/j.1750‐2659.2012.00350.x. Background Live attenuated influenza vaccines (LAIV) against a variety of strains of pandemic potential are being developed and tested. We describe the results of an open‐label phase I trial of a live attenuated H2N2 virus vaccine. Objectives To evaluate the safety, infectivity, and immunogenicity of a live attenuated H2N2 influenza virus vaccine. Participants/methods The A/Ann Arbor/6/60 (H2N2) virus used in this study is the attenuated, cold‐adapted, temperature‐sensitive strain that provides the genetic backbone of seasonal LAIV (MedImmune). We evaluated the safety, infectivity, and immunogenicity of two doses of 10⁷ TCID₅₀ of this vaccine administered by nasal spray 4 weeks apart to normal healthy seronegative adults. Results Twenty‐one participants received a first dose of the vaccine; 18 participants received a second dose. No serious adverse events occurred during the trial. The most common adverse events after vaccination were headache and musculoskeletal pain. The vaccine was restricted in replication: 24% and 17% had virus detectable by culture or rRT‐PCR after the first and second dose, respectively. Antibody responses to the vaccine were also restricted: 24% of participants developed an antibody response as measured by either hemagglutination‐inhibition assay (10%), or ELISA for H2 HA‐specific serum IgG (24%) or IgA (16%) after either one or two doses. None of the participants had a neutralizing antibody response. Vaccine‐specific IgG‐secreting cells as measured by enzyme‐linked immunospot increased from a mean of 0·5 to 2·0/10⁶ peripheral blood mononuclear cells (PBMCs); vaccine‐specific IgA‐secreting cells increased from 0·1 to 0·5/10⁶ PBMCs. Conclusions The live attenuated H2N2 1960 AA ca vaccine demonstrated a safety profile consistent with seasonal trivalent LAIV but was restricted in replication and minimally immunogenic in healthy seronegative adults.     

A(H9N2) influenza viruses associated with chicken mortality in outbreaks in Algeria 2017

In late 2017, increased mortality was detected in chicken farms in Algeria undergoing A(H9N2) influenza outbreaks. Analysis of viruses isolated from affected farms showed that they were monophyletic, were of the G1 hemagglutinin (HA) lineage, and were antigenically and genetically similar to viruses detected contemporaneously in other countries in Northern Africa and the Middle East. The virus was able to spread via contact transmission between ferrets but did not cause disease in intravenously inoculated chickens.     

云南省首例人感染H9N2禽流感病例发现与应对

目的对云南省流感监测中发现的首例人感染H9N2禽流感病例进行调查分析,为进一步防治人禽流感疫情提供科学依据。方法对患者、密切接触者和活禽市场开展流行病学调查,并采集病例呼吸道标本和外环境标本进行实验室检测分析。结果病例有活禽市场暴露史,标本禽流感病毒核酸阳性结果表明,该病例为人感染H9N2禽流感确诊病例,未出现二代病例。病例暴露的活禽市场环境中存在大量禽流感病毒。结论医疗机构加强流感样病例监测和不明原因肺炎监测是及时发现人禽流感病例的重要手段。活禽交易市场定期消毒与休市是降低感染率的关键措施。     

甲型H1N1流感患者免疫学指标分析

目的分析甲型H1N1流感患者免疫学指标的特点。方法以明确诊断的87例甲型H1N1流感患者为研究对象,比较疾病急性期、恢复期部分免疫学指标变化情况,并进行统计学分析。结果在病程急性期,淋巴细胞总数、GIN＋T淋巴细胞、CD8＋T淋巴细胞及B淋巴细胞计数明显下降。随着病情的恢复,以上指标均明显上升;总补体溶血活性CH50在整个病程中均处于较高水平。结论在甲型H1N1流感病程中,机体细胞免疫起着重要作用。     

Genetic analysis of H3N2 influenza A viruses isolated in 2006–2007 in Nairobi,Kenya

Background Minimal influenza surveillance has been carried out in sub‐Saharan Africa to provide information on circulating influenza subtypes for the purpose of vaccine production and monitoring trends in virus spread and mutations. Objective The aim of this study was to investigate a surveillance program in Kenya to isolate and characterize influenza viruses. Results In the 2006–2007 influenza season, nine influenza A viruses were isolated. All were of H3N2 subtype with key amino acid (aa) changes indicating that they were more closely related to recent World Health Organization recommended vaccine strains than to older vaccine strains, and mirroring the evolution of circulating influenza A globally. Hemagglutination inhibition data showed that the 2006 Kenya isolates had titers identical to the 2005–2006 H3N2 vaccine strain but two‐ to threefold lower titers to the 2006–2007 vaccine strain, suggesting that the isolates were antigenic variants of the 2006–2007 vaccine strains. Analysis of aa substitutions of hemagglutinin‐1 (HA1) protein of the 2006 Kenyan viruses revealed unique genetic variations with several aa substitutions located at immunodominant epitopes of the HA1 protein. These mutations included the V112I change at site E, the K 173 E substitution at site D and N 278 K change at site C, mutations that may result in conformational change on the HA molecule to expose novel epitopes thus abrogating binding of pre‐existing antibodies at these sites. Conclusion Characterization of these important genetic variations in influenza A viruses isolated from Kenya highlights the importance of continuing surveillance and characterization of emerging influenza drift variants in sub‐Saharan Africa.