Avian influenza ai, caused by the influenza virus typea, can affect several species of food producing birds. Avian influenza a virus constitutes a large threat to human health. Philippa, in zoo and wild animal medicine sixth edition, 2008. Wild birds worldwide carry the viruses in their intestines, but usually do not get. Lately, several zoonotic avian influenza a strains have been reported to directly infect humans. Avian pathology the onset of virus shedding and clinical signs in chickens infected with highpathogenicity and lowpathogenicity avian influenza viruses download pdf 364. Introduction highly pathogenic avian influenza hpai caused by the ah5n1 influenza subtype in animal. Avian influenza virus can survive for 100 days in distilled water at room temperature, and 200 days at 17 c 63 f.
The virus was first detected in 1996 in geese in china. Sixteen h subtypes and nine n subtypes of influenza a virus have been identified. Highly pathogenic avian influenza h5n1 outbreaks in poultry. Exciting, cuttingedge new methods focus on studying the virus itself and.
Pathology, molecular biology, and pathogenesis of avian influenza a. However, this possibility combined with the increasing resistance of the h5n1 ai virus to currently available antiviral treatment and lack of complete vaccination effectiveness make this a critical human health risk. Genesis and pathogenesis of the 1918 pandemic h1n1 influenza. Virusinduced pathogenesis, vaccine development, and diagnosis of novel h7n9 avian influenza a virus in humans. Avian influenza refers to the disease caused by infection with avian bird influenza flu type a viruses. The serotypes of influenza a virus are identified based on the hemagglutinin h and neuraminidase n proteins.
Asian h5n1 was first detected in humans in 1997 during a poultry outbreak in hong kong and has since been detected in. The authors of these studies postulated that in a fatal human infection with the avian h5n1 subtype, initial virus replication in the respiratory tract triggers hypercytokinemia complicated by a reactive hemophagocytic syndrome, which might be a different pathogenesis of influenza a h5n1 infection from that of usual human subtypes to 2001. Variable impact of the hemagglutinin polybasic cleavage site on virulence and pathogenesis of avian influenza h7n7 virus in chickens, turkeys and ducks. New human influenza a virus strains regularly emerge causing seasonal epidemics and occasional pandemics. Apoptosis and pathogenesis of avian influenza a h5n1 virus in humans article pdf available in emerging infectious diseases 5. Results of in vitro experiments support the role of an exaggerated immune response in the pathogenesis of h5n1 influenza. Highly pathogenic h5n1 virus has evolved, through a complexity of. Feb 12, 2020 avian influenza is caused by influenza a virus, which has 8 rna segments. Similar to the h5n1 virus, the 1918 influenza virus appears to be an avianlike virus rather than a reassortant. Mammalian pathogenesis and transmission of avian influenza a. We evaluated pathogenicity and transmission of representative viruses in mouse and ferret models and examined replication kinetics in. Avian influenza a virus aiv is a member of the orthomyxoviridae family and may be classified according to the antigenicity of its surface proteins hemagglutinin h and neuraminidase n, and on the basis of its pathogenicity in chickens after intravenous inoculation. Similarly, the pandemic of 1968 arose through the acquisition of a novel ha h3 and the pb1 gene from an avian source 6, 101. The avian virus is inactivated more quickly in manure, but can survive for up to 2 weeks in feces on cages.
Pathogenesis of avian influenza a h5n1 viruses in ferrets. However, it is possible that the most severely ill people are more likely to be diagnosed and reported, while milder cases are less likely to be. Phylogenetic analyses of six full gene segments and two partial gene segments obtained from next. Therefore, h5n1 virus has rightly received attention as a potential pandemic threat. In avian influenza virus, an expert team of researchers and diagnosticians examine the fundamental yet essential virological methods for ai virus research and diagnostics as well as some of the newest molecular procedures currently used for basic and applied research. Asian h5n1 was first detected in humans in 1997 during a poultry outbreak in hong kong and has since been detected in poultry and wild birds in more than 50 countries in. Avian influenza a h5n1 in humans differs in multiple ways from influenza due to human viruses, including the routes of transmission, clinical severity, pathogenesis, and perhaps, response to. Uiprasertkul m, kitphati tc, pathavathana p, et al. Seventeen avian species and two mammalian species were intranasally inoculated with the zoonotic achickenhong kong22097 chickenhk h5n1 avian influenza ai virus in order to ascertain a. Avian influenza the disease avian influenza ai is caused by specified viruses that are members of the family orthomyxoviridae and placed in the genus influenzavirus a. The pathogenesis of influenza in humans wiley online library. Introduction avian influenza ai viruses infect a wide variety of domestic poultry, captive birds, and freeranging wild bird species under natural and experimental conditions.
Avian influenza etiology pathogenesis and interventions avian influenza, sometimes avian flu, and commonly called bird flu, refers to influenza caused by viruses adapted to birds. More than a dozen types of bird flu have been identified, including the two strains that have most recently infected humans h5n1 and h7n9. There is no evidence to suggest that the consumption. Influenza virus infectivity, pathogenicity, and transmissibility in humans. Dowdle wr 1999 influenza a virus recycling revisited. Virusinduced pathogenesis, vaccine development, and.
Highly pathogenic asian avian influenza ah5n1 virus. The role of pb2 in the pathogenesis of h5n1 viruses. Highly pathogenic avian influenza a h5n1 viruses caused outbreaks of disease in domestic. Different routes of inoculation impact infectivity and pathogenesis of h5n1 high pathogenicity avian influenza virus infection in chickens and domestic ducks y. Bird flu is caused by a type of influenza virus that rarely infects humans. Aiv is characterized by its ability to undergo constant antigenic changes 1. In mouse models for infection with hpai h5n1 and hpai h7n7 viruses, this. Similar to the h5n1 virus, the 1918 influenza virus appears to be an avian like virus rather than a reassortant. Although several studies have shown some aspects of this pathogenesis in animal models, direct evidence of pathogenic mechanisms in humans has been limited to only a few autopsy studies. Avian influenza virus aiv is a member of the orthomyxoviridae family, influenzavirus a genus. Avian influenza etiology pathogenesis and interventions pdf.
Program pnsa manual for the contingency of avian influenza and. Avian influenza viruses are classified as either low pathogenic also called low pathogenicity avian influenza viruses or highly pathogenic high pathogenicity avian influenza viruses. Jul 10, 20 on 29 march 20, the chinese center for disease control and prevention confirmed the first reported case of human infection with an avian influenza ah7n9 virus 1. Pathology, molecular biology, and pathogenesis of avian.
Laboratoryadapted strains mainly produce spherical virions, whereas clinical isolates of human and equine strains of iav are mostly filamentous, thus suggesting that this latter virion. Pdf virusinduced pathogenesis, vaccine development, and. Collecting, preserving and shipping specimens for the diagnosis of avian influenza ah5n1 virus infection guide for field operations october 2006 4 1. Role of budding morphology in pathogenesis and transmission. Avian diseases avian influenza virus highly pathogenic avian influenza low pathogenic avian influenza pathobiology pathogenesis pathotypes. Avian influenza is a potential and unpredictable threat to humans because of the segmented nature of the genome. Global epidemiology of avian influenza a h5n1 virus infection in humans. The pathogenesis of avian influenza a h5n1 virus in humans is not well understood. The clinical manifestations, diagnosis, treatment, and prevention of avian influenza are discussed separately. Pathogenicity avian influenza virus infection in chickens and. Pdf pathogenesis and transmission of avian influenza a h7n9.
Highly pathogenic asian avian influenza ah5n1 in people. Influenza a virus is further classified on the basis of the surface glycoproteins, hemagglutinin ha or h and neuraminidase na or n. A virus is defined as hpai or lpai by its ability to cause severe disease in intravenously inoculated young chickens in the laboratory, or by. The characteristics of the aging immune system and possible, novel vaccine. N2, and pb1 genes from an avian virus 101, 120, 187, 252. Asian highly pathogenic avian influenza hpai a h5n1 virus occurs mainly in birds and is highly contagious among them. These influenza viruses occur naturally among birds. H5n1 avian influenza viruses induce significantly higher expression of several cytokines and chemokines in human macrophages and respiratory epithelial cells than human influenza viruses.
On 29 march 20, the chinese center for disease control and prevention confirmed the first reported case of human infection with an avian influenza ah7n9 virus. Apoptosis and pathogenesis of avian influenza a h5n1 virus in humans. Highly pathogenic asian avian influenza ah5n1 virus avian. Summary pandemic influenza virus has its origins in avian influenza viruses. Collecting, preserving and shipping specimens for the. Variable impact of the hemagglutinin polybasic cleavage site.
It continues to cross species barriers to infect humans and other mammals, often with fatal outcomes. A virus is defined as hpai or lpai by its ability to cause severe disease in intravenously inoculated young chickens in. Jun 02, 2009 pathogenesis of influenza in humans 2 june 2009 when influenza virus is introduced into the respiratory tract, by aerosol or by contact with saliva or other respiratory secretions from an infected individual, it attaches to and replicates in epithelial cells. Shope re 1936 the incidence of neutralizing antibodies for swine. Aiv envelope contains two major glycoproteins, hemagglutinin ha and neuraminidase na 2. Avian influenza viruses can survive indefinitely when frozen. A virus is defined as hpai or lpai by its ability to cause severe disease in intravenously inoculated young chickens in the laboratory, or by its. Avian influenza virus infection of domestic poultry produces syndromes ranging from asymptomatic infection to respiratory disease and a drop in egg production, to severe, systemic disease with near 100% mortality. These viruses occur naturally among wild aquatic birds worldwide and can infect domestic poultry and other bird and animal species. Jul 15, 2009 the first recognized case of human illness from infection with highly pathogenic avian influenza a h5n1 virus occurred in may 1997 1, 2, and 17 additional cases were detected in late 1997 in hong kong.
Apoptosis was observed in alveolar epithelial cells, which is the major target cell type for the viral replication. Rabadan r, levine aj, robins h 2006 comparison of avian and human influenza a viruses reveals a mutational bias on the viral genomes. This is a pdf file of an unedited manuscript that has been. Swaynebd aimport risk assessment division, national veterinary research and quarantine service, 480 anyang6 dong, anyang city, gyeonggi province, south korea. Update on avian influenza a h5n1 virus infection in humans. Influenza virus a influenza virus b influenza virus c thogotovirus isavirus baltimore classification. Similar to h5n1 viruses, human cases with h7n9 virus seem to result. Avian influenza, for most purposes, refers to the influenza a virus. Pleomorphism is a characteristic of influenza a virus iav, which can produce spherical particles of 100 nm in diameter and filaments up to 30. If h5n1 avian influenza virus is presumptively identified by one of the above direct methods, further work should be conducted using the enhanced bsl3 procedures described for culture. Pathogenesis and transmission of avian influenza a h7n9. In contrast, the pandemic of 1918 is believed to have arisen through the direct adaptation of a purely avian virus to. See clinical manifestations and diagnosis of avian influenza and avian influenza a h5n1.
Asian highly pathogenic avian influenza hpai ah5n1 virus occurs mainly in birds and is highly contagious among them. In 1997, the avian influenza a virus subtype h5n1 crossed the avianhuman. The epidemiology, transmission, pathogenesis, treatment, and prevention of avian influenza are discussed separately. Information on avian influenza avian influenza flu. When bird flu does strike humans, it can be deadly. Of the few avian influenza a viruses that have crossed the species barrier to infect humans, asian hpai h5n1 virus has caused the largest number of detected cases of severe disease and death in humans. Avian influenza virus with the growing global fear of a major pandemic, avian influenza virus research has increased greatly in importance during this young century.
Epidemiology, transmission, and pathogenesis of avian. Epidemiology, transmission, and pathogenesis of avian influenza. Avian influenza a viruses are designated as highly pathogenic avian influenza hpai or low pathogenicity avian influenza lpai based on molecular characteristics of the virus and the ability of the virus to cause disease and mortality in chickens in a laboratory setting. The present study reports the genetic characterization of a lowpathogenicity h9n2 avian influenza virus, initially from a pool and subsequently from individual faecal samples collected from chestnut teals anas castanea in southeastern australia. Of greatest concern is highly pathogenic avian influenza hpai. Aquatic birds provide the natural reservoir for influenza a viruses, but in general, avian influenza is asymptomatic in feral birds. Pdf on 29 march 20, the chinese center for disease control and. Apoptosis and pathogenesis of avian influenza a h5n1 virus. Variable impact of the hemagglutinin polybasic cleavage site on virulence and pathogenesis of avian influenza. Any new or reemergent human influenza strain with suspected pandemic potential should be treated as described for h5n1 avian influenza. H7n9 avian influenza virus aiv caused human infections in 20 in china. Direct transmission of the h5n1 viruses from birds to humans resulted in 18 documented cases of respiratory.
We evaluated pathogenicity and transmission of representative viruses in mouse and ferret models and examined replication kinetics in human respiratory tract cells. Human infection with highly pathogenic avian influenza a h5n1. We previously demonstrated in an autopsy case that alveolar epithelial cells are the major target cell type of this. However, available studies indicate that highly pathogenic viruses, such as the h5n1 strain, spread to. Diagnosis is by isolation and characterisation of the virus. Phylogenetic analyses indicate that h7n9 aiv is a novel reassortant strain with pandemic potential. Highly pathogenic avian h5n1 influenza viruses now appear to be endemic. Recent outbreaks of highly pathogenic avian influenza h5n1 virus in poultry and in humans have raised concerns that an influenza pandemic will occur in the near future. In avian influenza virus, an expert team of researchers and diagnosticians examine the fundamental yet essential virological methods for ai virus research and diagnostics as well as some of the newest. Though influenza a is adapted to birds, it can also stably adapt and sustain persontoperson transmission. Human infection with highly pathogenic avian influenza a. Presence and survival of the virus most strains of avian influenza virus are found only in the respiratory and gastrointestinal tracts of infected birds, and not in meat. In most cases, they resemble those of conventional influenza, including.
Pathogenicity of highly pathogenic avian influenza virus in mammals. Highly pathogenic and low pathogenic avian influenza a viruses. Signs and symptoms of bird flu may begin within two to seven days of infection, depending on the type. Infections with low pathogenicity and highly pathogenic avian influenza ah7n9 viruses affected poultry in 4 states in the southeastern united states in 2017. We studied autopsy specimens from 2 patients who died of infection with this virus. Avian influenza is caused by influenza a virus, which has 8 rna segments. The highly pathogenic avian influenza virus subtype h5n1 is already panzootic in poultry, with attendant economic consequences. Outbreaks of bird flu have occurred in asia, africa, north america and. Pathogenesis and pathobiology of avian influenza virus. However, available studies indicate that highly pathogenic viruses, such as the h5n1 strain, spread to virtually all parts of an infected bird, including meat.
Pathogenesis and pathobiology of avian influenza virus infection in birds author. In this article we will discuss about influenza viruses. In early 20, a novel avian influenza a virus h7n9 strain was discovered in china to cause severe respiratory disease in humans. Apoptosis and pathogenesis of avian influenza a h5n1. Influenza a virus highly pathogenic avian influenzah5n1 aabb.
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