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H5N1
H5N1 is an avian influenzavirus. It is a pandemicthreat. H5N1 fluis what is commonly meant when talking of "bird flu" or "avian influenza" and is a viral disease that causes illness in many species including humans. H5N1 is moving from areas where it is endemic to other parts of the world through migrating waterfowlwho can carry and spread H5N1 (sometimes without themselves becoming sick).[{{fullurl:Template:FULLPAGENAME}}#endnote_waterfowl] However, avian influenza is mostly spread through domestic poultry rather than by wild birds (movements of infected poultry and poultry products; and use of infected poultry manure as fertiliser and as feed in fish-farms and pig farms). Humans who get sick from H5N1 typically catch it from chickens who catch it from either other chickens or waterfowl(ducks and geese). H5N1 is mutating into genetic variations that are infecting species not previously known to carry H5N1, but not all of these variations can infect humans. It is endemicin birds in southeast Asia and is threatening to become endemic in birds in Turkey. Current evidence from the latest outbreaks in north, central and east Turkeyshow a hemagglutininmutation making H5N1 easier to pass from chickens to humans, but not yet easier to pass from human to human[{{fullurl:Template:FULLPAGENAME}}#endnote_trk_060112]. Species killed by H5N1 infection in this December 2005and January 2006outbreak in Turkey include humans, chickens, turkeys, ducks, geese, and pigeons[{{fullurl:Template:FULLPAGENAME}}#endnote_OIE_Turkey_12_01_2006]. As of January 11, 2006, 155 cases of infections in humans, resulting in 78 deaths, have been confirmed worldwide. Not all cases of H5N1 infection are reported and consequently the exact mortality rate is unknown. Earlier historical flu pandemics, which were also believed to be of avian origin, had reportedly an average mortality rate of 2.5-5%. Tens of millions of birds have died of H5N1 influenza and hundreds of millions of birds have been culled (slaughtered and disposed of) to protect humans from H5N1[2]. Countries that have reported one or more H5N1 outbreaks include (in order of first outbreak occurance): Korea, Vietnam, Japan, Thailand, Cambodia, Laos, Indonesia, China, Malaysia, Russia, Kazakhstan, Mongolia, Turkey, Romania, Croatia, Ukraine, Cyprus, and Iraq. [{{fullurl:Template:FULLPAGENAME}}#endnote_affected_countries_WHO] The current projected worst case scenario for a H5N1 pandemic is somewhere around 150,000,000 human deaths directly due to H5N1 infection (or two to three percent of the world's human population). No one knows what the chances are for this worst case scenario. Image:BirdFluWorld.png Image:Influenza A - late passage.jpg Image:H5N1.JPG
Avian Flu
H5N1 is a subtype of the species called avian influenza virus (bird flu). Avian flu is a disease and avian flu virus is a species. The avian flu virus subtypes are labeled according to an H number and an N number. The avian influenza subtypes that have been confirmed in humans, ordered by the number of known human deaths, are: H1N1caused "Spanish Flu", H2N2caused "Asian Flu", H3N2caused "Hong Kong Flu", H5N1 is the current pandemicthreat, H7N7has unusual zoonotic potential, H1N2is currently endemic in humans and pigs, H9N2, H7N2, H7N3, H10N7. The annual flu (also called "seasonal flu" or "human flu") kills an estimated 36,000 people in the United States each year. The dominant strain of annual flu virus in January 2006is H3N2which is now resistant to the standard antiviral drugs amantadineand rimantadine. Avian influenza virus H3N2is endemic in pigs ("swine flu") in China and has been detected in pigs in Vietnam, increasing fears of the emergence of new variant strains. Health experts say pigs can carry human influenza viruses, which can combine (i.e. exchange homologous genome sub-units by genetic reassortment.) with H5N1, swapping genes and mutating into a form which can pass easily among humans. A combination of these two subtypes of the species known as the avian fluvirus in a country like China is a worst case scenerio. Transmission and infection (H5N1 Flu)
Infected birds pass on H5N1 through their saliva, nasal secretions, and feces. Other birds may pick up the virus through direct contact with these excretions or when they have contact with surfaces contaminated with this material. Because migratory birds are among the carriers of the H5N1 virus it may spread to all parts of the world. Past outbreaks of avian flu have often originated in crowded conditions in southeastand east Asia, where humans, pigs, and poultry live in close quarters. In these conditions a virus can mutateinto a form that more easily infects humans. The current method of prevention in animal populations is to destroy infected animals, as well as animals suspected of being infected. In southeast Asia, millions of domestic birds have been slaughtered to prevent the spread of the virus. Since H5N1 is an influenza virus, symptomssimilar to those of the common flu, such as fever, cough, sore throat, and sore muscles, can develop in infected humans. However, in more severe cases, pneumoniaand respiratory failurecan develop and eventually cause death. Patients with H5N1 avian influenza have rarely had conjunctivitis[9], unlike human cases of infection by the H7viruses. Severe infection from H5N1 caused multiple lung infections (including pus, fever, cough), lung scar tissue, fluid in the space surrounding the lungs, enlarged lymph nodes and cavities forming in the lung tissue. Neuraminidase inhibitors are a class of drugs that includes zanamivirand oseltamivir, the latter being licensed for prophylaxistreatment in the United Kingdom. Oseltamivir inhibits the influenza virus from spreading inside the user's body [8]. It is marketed by Rocheas Tamiflu. This drug has become a focus for some governments and organizations trying to be seen as making preparations for a possible H5N1 pandemic. In August2005, Roche agreed to donate three million courses of Tamiflu to the World Health Organization, to be deployed by the WHO to contain a pandemic in its region of origin. Although Tamiflu is patented, international law gives governments wide freedom to issue compulsory licensesfor life-saving drugs. Global spreadImage:Wikinews-logo.png
Wikinewshas news related to this article:
Category:Avian Flu
"Since 1997, studies of influenza A (H5N1) indicate that these viruses continue to evolve, with changes in antigenicity and internal gene constellations; an expanded host range in avian species and the ability to infect felids; enhanced pathogenicity in experimentally infected mice and ferrets, in which they cause systemic infections; and increased environmental stability."[{{fullurl:Template:FULLPAGENAME}}#endnote_Global_Spread]
Preparations for a potential influenza pandemic
"[T]he United Statesis collaborating closely with eight international organizations, including the World Health Organization(WHO), the Food and Agriculture Organization of the United Nations(FAO), the World Organization for Animal Health(OIE), and 88 foreign governments to address the situation through planning, greater monitoring, and full transparency in reporting and investigating avian influenzaoccurrences. The United States and these international partners have led global efforts to encourage countries to heighten surveillance for outbreaks in poultry and significant numbers of deaths in migratory birds and to rapidly introduce containment measures. The U.S. Agency for International Development(USAID) and the U.S. Department of State, the U.S. Department of Health and Human Services(HHS), and Agriculture(USDA) are coordinating future international response measures on behalf of the White House with departments and agencies across the federal government." [{{fullurl:Template:FULLPAGENAME}}#endnote_usaid.gov] Together steps are being taken to "minimize the risk of further spread in animal populations", "reduce the risk of human infections", and "further support pandemic planning and preparedness".[{{fullurl:Template:FULLPAGENAME}}#endnote_usaid.gov] Ongoing detailed mutually coordinated onsite surveillance and analysis of human and animal H5N1 avian flu outbreaks are being conducted and reported by the USGSNational Wildlife Health Center, the Centers for Disease Control and Prevention, the World Health Organization, the European Commission, and others.[{{fullurl:Template:FULLPAGENAME}}#endnote_outbreaks] TechnicalH5N1 is a type of avian influenzavirus (bird flu virus) that has mutated[{{fullurl:Template:FULLPAGENAME}}#endnote_CDCWHO] through antigenic driftinto dozens of highly pathogenicvarieties, but all currently belonging to genotype Z of avian influenza virus H5N1. Genotype Z emerged through reassortmentin 2002from earlier highly pathogenicgenotypes of H5N1[{{fullurl:Template:FULLPAGENAME}}#endnote_workshop] that first appeared in Chinain 1996in birdsand in Hong Kongin 1997in humans[{{fullurl:Template:FULLPAGENAME}}#endnote_timeline]. The "H5N1 viruses from human infections and the closely related avian viruses isolated in 2004and 2005belong to a single genotype, often referred to as genotype Z." [1] This infection of humans coincided with an epizootic(an epidemicin nonhumans) of H5N1 influenza in Hong Kong?s poultry population. This panzootic (a disease affecting animals of many species especially over a wide area) outbreak was stopped by the killing of the entire domestic poultry population within the territory. The name H5N1 refers to the subtypes of surface antigenspresent on the virus: hemagglutinintype 5 and neuraminidasetype 1. Genotype Z of avian influenza virus H5N1 is now the dominant genotype of H5N1. Genotype Z is endemic in birds in southeast Asia and represents a long term pandemic threat. The species called the avian flu virus has a subtype called H5N1 which has a strain called highly pathogenic H5N1 which includes genotype or strain Z which has been divided into two genetic cladeswhich are known from specific isolates. Among H5N1 viruses, only clade one infects humans. Terminology"Virus" refers to either the complete virus assemblage or when distinguishing between its parts it refers to the molecules(RNAin the case of H5N1) comprising the genomethat is surrounded (encapsidated) by a protective coat of protein called a capsidwhich binds directly to the viral genome. This complex of protein and nucleic acid is called the nucleocapsid. The complete virus assemblage is referred to as a virion. In normal useage "H5N1 virus" refers to the H5N1 nucleocapsid which is the same as the H5N1 virion since the H5N1 lacks an envelope (a membranous lipid structure that surrounds the nucleocapsid). Avian influenzais not a genus of Orthomyxoviridae. The term "avian influenza" denotes a disease not a virus. The orthomyxovirus family consists of 5 genera: Influenzavirus A, Influenzavirus B, Influenzavirus C, Isavirus, and Thogotovirus. Influenzavirus A is not the same as "avian influenza": the former is a genus of viruses, the latter is an illness. In phylogeneticsbased taxonomythe "RNA viruses" includes the "negative-sense ssRNA viruses" which includes the Order "Mononegavirales" which includes the Family "Orthomyxoviridae" which contains five genera, classified by variations in nucleoprotein (NP and M) antigens. One of these is the Genus "Influenzavirus A" which consists of a single species (or "type species") called "Influenza A virus" (AI) and one of its subtypes is H5N1. H5N1 (like the other avian flu viruses) has strains called "highly pathogenic" (HP) and "low-pathogenic" (LP). "Avian influenza viruses that cause HPAI are highly virulent, and mortality rates in infected flocks often approach 100%. LPAI viruses are generally of lower virulence, but these viruses can serve as progenitors to HPAI viruses. The current strain of H5N1 responsible for die-offs of domestic birds in Asia is an HPAI strain; other strains of H5N1 occurring elsewhere in the world are less virulent and, therefore, are classified as LPAI strains. All HPAI strains identified to date have involved H5 and H7 subtypes." The species called the avian flu virus has a subtype called H5N1 which has a strain called highly pathogenic H5N1 which includes genotype or strain Z which has been divided into two genetic clades which are known from specific isolates. Only clade one infects humans but all clade one are resistant to adamantanes. Each specific known genetic variation is known from a virus isolate of a specific case of infection.[{{fullurl:Template:FULLPAGENAME}}#endnote_Terminology] Influenza virus isolates are notated as in this example: A/New York/348(H1N2):
H5N1 virus structure
A virusis one type of microscopic parasitethat infectscellsin biological organisms.
The Orthomyxoviridaeare a family of RNA viruseswhich infect vertebrates. It includes those viruseswhich cause influenza. Viruses of this family contain 7 to 8 segments of linear negative-sense single stranded RNA.
"Influenza virus" refers to a subset of Orthomyxoviridaethat create influenza. This is not a phylogeneticsbased taxonomiccategory.
Avian influenza(also known as bird flu, avian flu, influenza virus A flu, type A flu, or genus A flu) is a flu due to a type of influenzavirusthat is hosted by birds, but may infect several species of mammals. The avian influenzavirus subtypes that have been confirmed in humans, ordered by the number of known human deaths, are: H1N1 caused Spanish flu, H2N2 caused Asian Flu, H3N2 caused Hong Kong Flu, H5N1, H7N7, H9N2, H7N2, H7N3. Avian influenza viruses have 10 geneson eight separate RNA molecules (called: PB2, PB1, PA, HA, NP, NA, M, and NS). HA, NA, and M specifythe structure of proteins that are most medically relevant as targets for antiviral drugs and antibodies. This segmentation of the influenza genomefacilitates genetic recombinationby segment reassortment in hosts who are infected with two different influenza viruses at the same time[1]. Avian influenza viruses compose the Influenzavirus A genusof the Orthomyxoviridaefamily and are negative sense, single-stranded, segmented RNA viruses. "The influenza virus RNA polymerase is a multifunctional complex composed of the three viral proteins PB1, PB2 and PA, which, together with the viral nucleoprotein NP, form the minimum complement required for viral mRNA synthesis and replication."[{{fullurl:Template:FULLPAGENAME}}#endnote_structure2]
The hemagglutinin, neuraminidase, and M2 proteinsare essential viral proteins with functions that can be inhibited by antiviral drugs such as oseltamivir and rimantadine or bound by virus-inactivating antibodies produced by the immune system. Influenzaviruses have a relatively high mutation rate that is characteristic of RNA viruses. The H5N1 virus has mutated into a variety of types with differing pathogenic profiles; some pathogenic to one species but not others, some pathogenic to multiple species[{{fullurl:Template:FULLPAGENAME}}#endnote_variants]. The ability of various influenza strains to show species-selectivity is largely due to variation in the hemagglutinin genes. Genetic mutationsin the hemagglutinin gene that cause single amino acidsubstitutions can significantly alter the ability of viral hemagglutinin proteins to bind to receptorson the surface of host cells. Such mutations in avian H5N1 viruses can change virus strains from being inefficient at infecting human cells to being as efficient in causing human infections as more common human influenza virus types[{{fullurl:Template:FULLPAGENAME}}#endnote_specificity]. This doesn't mean one amino acid substitution can cause a pandemic but it does mean one amino acid substitution can cause an avian flu virus that is not pathogenic in humans to become pathogenic in humans. In July2004, researchers led by H. Deng of the Harbin Veterinary Research Institute, Harbin, China and Professor Robert Websterof the St Jude Children's Research Hospital, Memphis, Tennessee, reported results of experiments in which micehad been exposed to 21 isolates of confirmed H5N1 strains obtained from ducks in China between 1999and 2002. They found "a clear temporal pattern of progressively increasing pathogenicity"[{{fullurl:Template:FULLPAGENAME}}#endnote_ducks]. Results reported by Dr. Webster in July 2005reveal further progression toward pathogenicity in mice and longer virus shedding by ducks. Recent research of Taubenberger et al [{{fullurl:Template:FULLPAGENAME}}#endnote_Taubenberger] has shown that the 1918 virus, like H5N1, was also an avian influenza virus. Furthermore, Tumpey and colleagues [{{fullurl:Template:FULLPAGENAME}}#endnote_Tumpey] who reconstructed the H1N1 virus of 1918 came to the conclusion that it is was most notably the polymerase genes and the HA and NA genes that caused the extreme virulence of this virus. The sequences of the polymerase proteins (PA, PB1, and PB2) of the 1918virus and subsequent human viruses differ by only 10 amino acids from the avian influenza viruses. Human forms of seven of the ten amino acids have already been identified in currently circulating H5N1. It is not unlikely that the other mutations eventually will surface and make the H5N1 virus capable of human-to-human transmission. Another important factor is the change of the HA protein to a binding preference for alpha 2,6 sialic acid (the major form in the human respiratory tract). In avian virus the HA protein preferentially binds to alpha 2,3 sialic acid, which is the major form in the avian enteric tract. It has been shown that only a single amino acid change can result in the change of this binding preference. Altogether, only a handful of mutations need to take place in order for H5N1 avian flu to become a pandemic virus like the one of 1918. See also
Sources
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|else=a}} Full text article online: "Avian Influenza A (H5N1) Infection in Humans" by The Writing Committee of the World Health Organization (WHO) Consultation on Human Influenza A/H5 in New England Journal of Medicine (29 September2005) Volume 353 pages 1374-1385.
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|else=a}} Oseltamivir (Tamiflu) informationfrom United States National Institutes of Health. Webpage content initially developed on January 13, 2000 and revised on January 10, 2001.
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|else=b}} Evolution of H5N1 avian influenza viruses in Asiaby The World Health Organization Global Influenza Program Surveillance Network in Emerging Infectious Diseases (2005). See Figure 1for a diagramatic representation of the genetic relatedness of Asian H5N1 hemagglutiningenes from various isolates of the virus.
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|else=a}} "The Threat of Pandemic Influenza: Are We Ready?" Board on Global Health Workshop Summary (2005). See page 118for a map and page 123for a diagram of reassortment of viral genes. The bird culls are described on page 116.
Further reading
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Moved to Global spread of H5N1. Add there.de:Influenza A/H5N1 es:H5N1 fr:H5N1 is:H5N1 nl:H5N1 no:H5N1 sr:?5?1 ru:?????? ?????-H5N1 fi:H5N1 vi:H5N1 zh:H5N1??
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