Influenza A: From highly pathogenic H5N1 to pandemic 2009 H1N1. Epidemiology and clinical features

The last decade has seen the emergence of two new influenza A subtypes and they have become a cause of concern for the global community. These are the highly pathogenic H5N1 influenza A virus (H5N1) and the Pandemic 2009 influenza H1N1 virus. Since 2003 the H5N1 virus has caused widespread disease and death in poultry, mainly in south East Asia and Africa. In humans the number of cases infected with this virus is few but the mortality has been about 60%. Most patients have presented with severe pneumonia and acute respiratory distress syndrome. The second influenza virus, the pandemic H1N1 2009, emerged in Mexico in March this year. This virus acquired the ability for sustained human to human spread and within a few months spread throughout the world and infected over 4 lakh individuals. The symptoms of infection with this virus are similar to seasonal influenza but it currently affecting younger individuals more often. Fortunately the mortality has been low. Both these new influenza viruses are currently circulating and have different clinical and epidemiological characteristics.     

一起农村小学甲型H3N2流感暴发流行的调查分析

目的了解甲型H3N2流感暴发流行特征,为制定预防措施提供依据。方法对和温村小学239名学生流感发病及流感疫苗接种情况进行调查,对发病者逐一个案调查登记,采集患者咽拭子标本送百色市疾病预防控制中心实验室检测确诊。结果该校学生流感发病33例,发病率为13.81%,学前班及1~6年级共7个班均有病例发生,发病班级为100%。发病者中,男性18例,女性15例,男女性别比为1.2∶1,男女发病率分别为14.52%(18/124)、13.04%(15/115),(χ2=0.11,P0.05),男女发病率差异无统计学意义。患者咽拭子标本5人份,经实验室检测甲型H3N2流感病毒核酸阳性率为100%。结论该校学生无流感疫苗免疫接种史,易感人群积累,是本次甲型H3N2流感暴发流行的根本原因。应在每年秋冬流感流行季节前一个月,加强中小学校学生流感疫苗接种,提高易感人群免疫力,防止甲型H3N2流感扩散蔓延。     

引发2009年流感暴发的H1N1新型流感病毒的研究进展

引起流感世界性大流行的主要原因与流感病毒表面抗原血凝素(HA)和神经氨酸酶(NA)频发的变异有很大关系,抗原的变异使得流感病毒可以逃逸机体的免疫防御,而且使许多应用中的疫苗失去防御效果。综述2009年世界暴发的H1N1新型流感病毒的结构在进化过程中发生的变异,有助于增加人们对流感病毒的了解,从而有效的治疗和预防流感大流行。     

Diagnosis of influenza viruses with special reference to novel H1N1 2009 influenza virus

On 15 April and 17 April 2009, novel swineorigin influenza A (H1N1) virus was identifi ed in specimens obtained from two epidemiologically unlinked patients in the United States. The ongoing outbreak of novel H1N1 2009 influenza (swine influenza) has caused more than 3,99,232 laboratory confi rmed cases of pandemic influenza H1N1 and over 4735 deaths globally. This novel 2009 influenza virus designated as H1N1 A/swine/California/04/2009 virus is not zoonotic swine flu and is transmitted from person to person and has higher transmissibility then that of seasonal influenza viruses. In India the novel H1N1 virus infection has been reported from all over the country. A total of 68,919 samples from clinically suspected persons have been tested for influenza A H1N1 across the country and 13,330 (18.9%) of them have been found positive with 427 deaths. At the All India Institute of Medical Sciences, New Delhi India, we tested 1096 clinical samples for the presence of novel H1N1 influenza virus and seasonal influenza viruses. Of these 1096 samples, 194 samples (17.7%) were positive for novel H1N1 influenza virus and 197 samples (18%) were positive for seasonal influenza viruses. During outbreaks of emerging infectious diseases accurate and rapid diagnosis is critical for minimizing further spread through timely implementation of appropriate vaccines and antiviral treatment. Since the symptoms of novel H1N1 influenza infection are not specifi c, laboratory confi rmation of suspected cases is of prime importance.     

Immunogenic and protective properties of the first kazakhstan vaccine against pandemic influenza A (H1N1) pdm09 in Ferrets

This paper presents the results of a pre-clinical study of the immunogenicity and efficacy of an egg-derived, inactivated, whole-virion adjuvanted vaccine (Refluvac®) on ferret models. For this purpose, groups of eight ferrets (6 to 7 months old) were injected with 0.5 mL of vaccine specimens containing 3.75, 7.5 or 15.0 μg of virus hemagglutinin. Administration was intramuscular and given either as a single dose or as two doses 14 days apart. All vaccine specimens manifested immunogenicity in ferrets for single (HI titer, from 51 ± 7 to 160 ± 23) and double (HI titer, from 697 ± 120 to 829 ± 117) administrations. To assess the protective effects of the vaccine, ferrets from the vaccinated and control groups were infected intranasally with pandemic virus A/California/7/09 (H1N1) pdm09 at a dose of 10⁶ EID₅₀/0.5 mL. Fourteen days post-infection, the ferrets inoculated with single or double vaccines containing 3.75, 7.5 or 15.0 μg of hemagglutinin per dose showed no signs of influenza infection, weight loss, or body temperature rise, and no premature deaths occurred. The number of vaccinated ferrets shedding the virus via the upper airway, as well as the amount of virus shed after infection, was significantly reduced in comparison with animals from the control group. Based on our results, we suggest that a single vaccination at a dose of 3.75 or 7.5 μg hemagglutinin be used for Phase I clinical trials.     

Swine-origin influenza-virus-induced acute lung injury: Novel or classical pathogenesis?

Influenza viruses are common respiratory pathogens in humans and can cause serious infection that leads to the development of pneumonia. Due to their host-range diversity, genetic and antigenic diversity, and potential to reassort genetically in vivo, influenza A viruses are continual sources of novel influenza strains that lead to the emergence of periodic epidemics and outbreaks in humans. Thus, newly emerging viral diseases are always major threats to public health. In March 2009, a novel influenza virus suddenly emerged and caused a worldwide pandemic. The novel pandemic influenza virus was genetically and antigenically distinct from previous seasonal human influenza A/H1N1 viruses; it was identified to have originated from pigs, and further genetic analysis revealed it as a subtype of A/H1N1, thus later called a swine-origin influenza virus A/H1N1. Since the novel virus emerged, epidemiological surveys and research on experimental animal models have been conducted, and characteristics of the novel influenza virus have been determined but the exact mechanisms of pulmonary pathogenesis remain to be elucidated. In this editorial, we summarize and discuss the recent pandemic caused by the novel swine-origin influenza virus A/H1N1 with a focus on the mechanism of pathogenesis to obtain an insight into potential therapeutic strategies.     

某高校甲型H1N1 流感确诊病例流行病学分布特征分析

目的：通过了解某高校甲型H1N1 流感病例的流行病学分布特征,为预防和控制流感在高校的蔓延提供依据。方法：以某高 校2009 年11 月6 日至2009 年11 月24 日发病并确诊的74 例甲型H1N1 流感病例为研究对象,分析并比较病例的年龄、性别、 学历层次、年级、专业、发病时间和临床症状。结果：74 例甲型H1N1 流感确诊病例均为学生,罹患率为1.63 %,其中男性占94.6 %,女性占5.4 %;病例平均年龄为20.5 岁± 2.2 岁;94.6 %的病例为本科生;本科生罹患率（4.03%）显著高于研究生（0.14%）;2006 级见习期本科生罹患率（11.05 %）显著高于其他年级学生;疫情的流行全距为19 天,发病高峰为2009 年11 月13 日至2009 年 11 月18 日;病例以发热、咳嗽、乏力、头疼等临床症状为主。结论：该高校甲型H1N1 流感确诊病例多为22岁以下的男性学生。本 研究提示加强见习学生的监测和管理、设立隔离宿舍、接种疫苗等有针对性的措施能够有效控制流感疫情在高校蔓延。     

Swine-origin pandemic H1N1 influenza virus-like particles produced in insect cells induce hemagglutination inhibiting antibodies in BALB/c mice

Recent outbreaks of influenza A highlight the importance of rapid and sufficient supply for pandemic and inter-pandemic vaccines. Classical manufacturing methods for influenza vaccines fail to satisfy this demand. Alternatively, cell culture-based production systems and virus-like particle (VLP)-based technologies have been established. We developed swine-origin pandemic H1N1 influenza VLPs consisting of hemagglutinin (A/California/04/2009) and matrix protein. Hemagglutinin and matrix protein were co-expressed in insect cells by the baculovirus expression system. VLPs were harvested from infection supernatants, purified and used for intraperitoneal immunization of BALB/c mice. Immunization induced high serum antibody titers against A/California/04/2009 as well as hemagglutination inhibiting antibodies. Additionally, we compared VLP production in two different insect cell lines, Sf9 and BTI-TN5B1-4 (High Five™). Taken together VLPs represent a potential strategy for the fight against new pandemic influenza viruses.     

基于分子对接技术筛选中草药中潜在的H1N1病毒神经氨酸酶抑制剂

甲型H1N1流感病毒是一种高度接触性急性呼吸道传染病,给人类健康造成了极大威胁。作为一个已经被证明的抗流感药物靶点,神经氨酸酶在流感病毒复制和传播中发挥重要作用,并且其活性中心的氨基酸组成高度保守。本研究中,我们使用分子对接技术筛选从中草药小分子数据库中筛选神经氨酸酶潜在的抑制剂,结果得到4个亲和力高于奥司他韦(Osel-tamivir)的化合物,并确定了他们的中草药来源。为从草药中提取,设计以及实验合成新的神经氨酸酶抑制剂提供了一定的依据和指导。     

Early induction of interleukin-5 and peripheral eosinophilia in acute pneumonia in Japanese children infected by pandemic 2009 influenza A in the Tokyo area

A novel influenza A (2009 H1N1) virus has led to a worldwide pandemic. A significant number of patients with pneumonia have been reported, although its pathogenesis remains to be elucidated. To determine its pathogenesis, we evaluated serum interleukin (IL)-5 and peripheral eosinophil counts in patients with acute pneumonia caused by the 2009 H1N1 virus. During the period from October to December 2009, 40 patients with laboratory-confirmed 2009 H1N1 pneumonia were under investigation. Their mean age at presentation was 6.8 years. The most characteristic finding was the early development of hypoxemic respiratory distress in the first 24 hr after the onset of fever. Bronchial mucous plugs included eosinophils in addition to neutrophils, even in patients without allergies. Serum IL-5 levels were elevated in 20 out of 24 patients (83%) whose samples were obtained in the first 24 hr after the onset of fever (26.5 ± 20.1 pg/mL), independent of the presence of underlying allergies. In contrast, induction of IL-5 was not documented in sera from eight patients with laboratory-confirmed 2009 H1N1 virus who developed neurological complications, but without lower respiratory infection (2.1 ± 0.7 pg/mL, P < 0.001 vs acute pneumonia). Peripheral eosinophilia was characteristic in acute pneumonia, but not in patients without a lower respiratory infection. There was a marked difference in the induction of IL-5 in 2009 H1N1 patients who developed acute pneumonia, compared with those without a lower respiratory infection. IL-5 may play a role in the early phase of acute pneumonia caused by the 2009 H1N1 virus in Japanese children.     

某高校甲型H1N1流感确诊病例流行病学分布特征分析

目的：通过了解某高校甲型H1N1流感病例的流行病学分布特征,为预防和控制流感在高校的蔓延提供依据。方法：以某高校2009年11月6日至2009年11月24日发病并确诊的74例甲型H1N1流感病例为研究对象,分析并比较病例的年龄、性别、学历层次、年级、专业、发病时间和临床症状。结果：74例甲型H1N1流感确诊病例均为学生,罹患率为1．63％,其中男性占94．6％,女性占5．4％;病例平均年龄为20．5岁±2．2岁;94．6％的病例为本科生;本科生罹患率（4．03％）显著高于研究生（0．14％）;2006级见习期本科生罹患率（11．05％）显著高于其他年级学生;疫情的流行全距为19天,发病高峰为2009年11月13日至2009年11月18日;病例以发热、咳嗽、乏力、头疼等临床症状为主。结论：该高校甲型H1N1流感确诊病例多为22岁以下的男性学生。本研究提示加强见习学生的监测和管理、设立隔离宿舍、接种疫苗等有针对性的措施能够有效控制流感疫情在高校蔓延。     

Hemagglutinin and neuraminidase matching patterns of two influenza A virus strains related to the 1918 and 2009 global pandemics

The current pandemic influenza A (H1N1) virus has revealed a complicated reassortment of various influenza A viruses. The biological study of these viruses, especially of the viral envelope proteins hemagglutinin (HA) and neuraminidase (NA), is urgently needed for the control and prevention of H1N1 viruses. We have generated H1N1-2009 and H1N1-1918 pseudotyped particles (pp) with high infectivity. Combinations of HA1918 + NA2009 and HA2009 + NA1918 also formed infectious H1N1pps, among which the HA2009 + NA1918 combination resulted in the most highly infectious pp. Our study demonstrated that some reassortments of H1N1 viruses may hold the potential to produce higher infectivity than do their ancestors.     

Molecular events leading to the creation of a pandemic influenza virus

Influenza A virus is a potent pathogen of annual respiratory illness with huge potential of causing occasional pandemics of catastrophic consequences. In April 2009, a novel, swine-origin influenza A H1N1/09 virus was identified in Mexico which continued to spread globally. This unique virus emerged from an avian, human, Eurasian swine viral strain and a North American swine strain belonging to the lineage of the 1930 swine virus. Till date H1N1/09 pandemic has been relatively mild and lacks the previously described molecular markers of influenza A pathogenicity and transmissibility. In this review, we will discuss the molecular and antigenic determinants of this virus and its designation as a low pathogenic strain, which carries the potential to develop into a devastating strain with subsequent mutations and reassortments.     

Pandemic swine influenza virus (H1N1): A threatening evolution

“Survival of the fittest” is an old axiom laid down by the great evolutionist Charles Darwin and microorganisms seem to have exploited this statement to a great extent. The ability of viruses to adapt themselves to the changing environment has made it possible to inhabit itself in this vast world for the past millions of years. Experts are well versed with the fact that influenza viruses have the capability to trade genetic components from one to the other within animal and human population. In mid April 2009, the Centers for Disease Control and Prevention and the World Health Organization had recognized a dramatic increase in number of influenza cases. These current 2009 infections were found to be caused by a new strain of influenza type A H1N1 virus which is a re-assortment of several strains of influenza viruses commonly infecting human, avian, and swine population. This evolution is quite dependent on swine population which acts as a main reservoir for the reassortment event in virus. With the current rate of progress and the efforts of heath authorities worldwide, we have still not lost the race against fighting this virus. This article gives an insight to the probable source of origin and the evolutionary progress it has gone through that makes it a potential threat in the future, the current scenario and the possible measures that may be explored to further strengthen the war against pandemic.     

Molecular characterization of avian-like H1N1 swine influenza a viruses isolated in Eastern China, 2011

Currently, three predominant subtypes of influenza virus are prevalent in pig populations worldwide: H1N1, H3N2, and H1N2. European avian-like H1N1 viruses, which were initially detected in European pig populations in 1979, have been circulating in pigs in eastern China since 2007. In this study, six influenza A viruses were isolated from 60 swine lung samples collected from January to April 2011 in eastern China. Based on whole genome sequencing, molecular characteristics of two isolates were determined. Phylogenetic analysis showed the eight genes of the two isolates were closely related to those of the avian-like H1N1 viruses circulating in pig populations, especially similar to those found in China. Four potential glycosylation sites were observed at positions 13, 26, 198, 277 in the HA1 proteins of the two isolates. Due to the presence of a stop codon at codon 12, the isolates contained truncated PB1-F2 proteins. In this study, the isolates contained 591Q, 627E and 701N in the polymerase subunit PB2, which had been shown to be determinants of virulence and host adaptation. The isolates also had a D rather than E at position 92 of the NS1, a marker of mammalian adaptation. Both isolates contained the GPKV motif at the PDZ ligand domain of the 3′ end of the NS1, a characteristic marker of the European avian-like swine viruses since about 1999, which is distinct from those of avian, human and classical swine viruses. The M2 proteins of the isolates have the mutation (S31N), a characteristic marker of the European avian-like swine viruses since about 1987, which may confer resistance to amantadine and rimantadine antivirals. Our findings further emphasize the importance of surveillance on the genetic diversity of influenza A viruses in pigs, and raise more concerns about the occurrence of cross-species transmission events.     

A/H1N1流感—世界关注的焦点

2009年4月,A/H1N1流感在墨西哥和美国暴发。随后,疫情迅速蔓延到美洲、欧洲、亚洲多个国家。A/H1N1流感病毒是一种以前在人或动物身上从未观测到的新病毒。遗传进化和抗原特性分析表明该病毒和猪流感病毒密切相关,与人类的季节性流感病毒有明显区别。但是流行病学信息表明A/H1N1流感病毒只攻击人类,并在人与人之间传播,尚未发现动物向人类传播的情况。本文从A/H1N1流感病毒的生物学特性、临床特征、公共卫生意义等方面全面阐述了A/H1N1流感的最新研究进展,为正确认识和科学防控A/H1N1流感提供参考。     

甲型H1N1流感病毒佐剂疫苗小鼠免疫效果

为了探讨甲型H1N1流感病毒氢氧化铝佐剂疫苗对小鼠的免疫作用及对小鼠繁殖性能的影响,以不同剂量、不同免疫程序免疫小鼠后定期采血;用血凝抑制(HI)方法检测血清H1N1流感病毒HI抗体滴度,观察H1N1流感病毒佐剂疫苗对小鼠受孕、产仔、哺乳的影响;比较孕鼠及非孕鼠的抗体滴度,免疫后孕鼠所产仔鼠的体重及H1N1胎传抗体水平。结果显示,以0.5μg组开始的不同剂量、不同免疫程序均可使小鼠产生90倍以上水平的H1N1流感病毒抗体;免疫后的小鼠不影响受孕、产仔及哺乳;仔鼠保护性抗体可持续1个月以上。H1N1流感病毒佐剂疫苗是一种高免疫原性的制剂,用低剂量免疫,即可产生90倍以上持续时间较长的保护性抗体。这种佐剂疫苗对小鼠的繁殖性能无明显影响,免疫产生的抗体经胎盘可垂直传递给仔鼠。     

温州地区人群对甲型H1N1流感认知情况及其疫苗不良反应的调查

目的了解温州地区居民对甲型H1N1流感(以下简称甲流)的认知情况及其疫苗的不良反应,分析相关调查数据为医务人员加强疾病防控提供依据。方法采用自行设计问卷,随机抽取2010年3月-4月温州地区居民888人为调查对象,对其进行问卷调查。结果温州地区人群对甲流及其疫苗的认知程度平均得分为15.69分,处于中低水平,各年龄段、各职业人群在认知度上差异存在统计学意义(P<0.05),走访的113名70岁以上的老人在甲型H1N1信息上欠缺认识。调查对象中50.5%人群对甲流疫苗的安全性持质疑观望态度。调查对象中共115人已接种疫苗,13人出现不良反应,占11.3%。结论甲流疫苗具有较高的安全性,但温州地区人群对甲型H1N1流感相关知识了解欠缺,而且群众的信任度不高,因此仍应加大宣传力度,尤其加强对老年人的预防宣教。JP     

甲型H1N1流感病毒HA蛋白结构和功能研究进展

自2009年3月,甲型H1N1流感疫情相继在包括我国在内的许多国家暴发,对人体健康和社会经济发展造成了严重危害。血凝素（HA）蛋白是重要的病毒表面糖蛋白,主要有3种功能：①与宿主细胞表面受体结合;②引起病毒包膜与靶细胞间的膜融合;③刺激机体产生中和性抗体。本文综合了近年来的研究成果,对甲型H1N1流感病毒HA蛋白结构、主要功能、进化、抗原性的研究进展进行了综述。     

Molecular distribution of amino acid substitutions on neuraminidase from the 2009 (H1N1) human influenza pandemic virus

The pandemic influenza AH1N1 (2009) caused an outbreak of human infection that spread to the world. Neuraminidase (NA) is anantigenic surface glycoprotein, which is essential to the influenza infection process, and is the target of anti-flu drugs oseltamivirand zanamivir. Currently, NA inhibitors are the pillar pharmacological strategy against seasonal and global influenza. Althoughmutations observed after NA-inhibitor treatment are characterized by changes in conserved amino acids of the enzyme catalyticsite, it is possible that specific amino acid substitutions (AASs) distant from the active site such as H274Y, could confer oseltamiviror zanamivir resistance. To better understand the molecular distribution pattern of NA AASs, we analyzed NA AASs from allavailable reported pandemic AH1N1 NA sequences, including those reported from America, Africa, Asia, Europe, Oceania, andspecifically from Mexico. The molecular distributions of the AASs were obtained at the secondary structure domain level for boththe active and catalytic sites, and compared between geographic regions. Our results showed that NA AASs from America, Asia,Europe, Oceania and Mexico followed similar molecular distribution patterns. The compiled data of this study showed that highlyconserved amino acids from the NA active site and catalytic site are indeed being affected by mutations. The reported NA AASsfollow a similar molecular distribution pattern worldwide. Although most AASs are distributed distantly from the active site, thisstudy shows the emergence of mutations affecting the previously conserved active and catalytic site. A significant number ofunique AASs were reported simultaneously on different continents.