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Avian influenza — known informally as ''avian flu'' or bird flu — refers to "influenza caused by viruses adapted to birds."〔"Avian influenza strains are those well adapted to birds"(EUROPEAN CENTRE FOR DISEASE PREVENTION AND CONTROL ).〕〔(Chapter Two : Avian Influenza by Timm C. Harder and Ortrud Werner ) in ''Influenza Report 2006''〕〔(Large-scale sequencing of human influenza reveals the dynamic nature of viral genome evolution ) Nature magazine presents a summary of what has been discovered in the Influenza Genome Sequencing Project.〕〔(Avian Influenza A (H5N1) Infection in Humans ) by The Writing Committee of the World Health Organization (WHO) Consultation on Human Influenza A/H5 in the September 29, 2005 New England Journal of Medicine〕〔(The Threat of Pandemic Influenza: Are We Ready? Workshop Summary (2005) ) Full text of online book by INSTITUTE OF MEDICINE OF THE NATIONAL ACADEMIES〕〔() CDC has a phylogenetic tree showing the relationship between dozens of highly pathogenic varieties of the Z genotype of avian flu virus H5N1 and ancestral strains.〕 The type with the greatest risk is highly pathogenic avian influenza (HPAI). "Bird flu" is a phrase similar to "swine flu," "dog flu," "horse flu," or "human flu" in that it refers to an illness caused by any of many different strains of influenza viruses that have adapted to a specific host. All known viruses that cause influenza in birds belong to the species ''influenza A virus''. All subtypes (but not all strains of all subtypes) of influenza A virus are adapted to birds, which is why for many purposes avian flu virus ''is'' the influenza A virus. (Note, however, that the "A" does ''not'' stand for "avian"). Adaptation is not exclusive. Being adapted toward a particular species does not preclude adaptations, or partial adaptations, toward infecting different species. In this way, strains of influenza viruses are adapted to multiple species, though may be preferential toward a particular host. For example, viruses responsible for influenza pandemics are adapted to both humans and birds. Recent influenza research into the genes of the Spanish flu virus shows it to have genes adapted to both birds and humans, with more of its genes from birds than less deadly later pandemic strains. While its most highly pathogenic strain (H5N1) had been spreading throughout Asia since 2003, avian influenza reached Europe in 2005, and the Middle East, as well as Africa, the following year.〔Monke, Jim. "Avian Influenza: Agricultural Issues." CRS Report for Congress. RS21747. August 29, 2006.〕 On January 22, 2012, China reported its second human death due to bird flu in a month following other fatalities in Vietnam and Cambodia.〔(China reports second bird flu death in a month - Health - Cold and flu - msnbc.com ) 〕 Companion birds in captivity and parrots are highly unlikely to contract the virus, and there has been no report of a companion bird with avian influenza since 2003. Pigeons do not contract or spread the virus.〔(【引用サイトリンク】title=Avian Influenza in Pigeons )〕 84% of affected bird populations are composed of chicken and farm birds, while the 15% is made up of wild birds according to capture-and-release operations in the 2000s, during the SARs pandemic. The first deadly Canadian case was confirmed on January 3, 2014. On December 2, 2014, two turkey farms in British Columbia, Canada, had been placed under quarantine after the Canadian Food Inspection Agency confirmed an avian flu outbreak. ==Genetics== Genetic factors in distinguishing between "human flu viruses" and "avian flu viruses" include: :PB2: (RNA polymerase): Amino acid (or residue) position 627 in the PB2 protein encoded by the PB2 RNA gene. Until H5N1, all known avian influenza viruses had a Glu at position 627, while all human influenza viruses had a Lys. :HA: (hemagglutinin): Avian influenza HA viruses bind alpha 2-3 sialic acid receptors, while human influenza HA viruses bind alpha 2-6 sialic acid receptors. Swine influenza viruses have the ability to bind both types of sialic acid receptors. Hemagglutinin is the major antigen of the virus against which neutralizing antibodies are produced, and influenza virus epidemics are associated with changes in its antigenic structure. This was originally derived from pigs, and should technically be referred to as "pig flu". 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Avian influenza」の詳細全文を読む スポンサード リンク
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