Abstract
Since its identification in April 2009, an A(H1N1) virus containing a unique combination of gene segments from both North American and Eurasian swine lineages has continued to circulate in humans. The lack of similarity between the 2009 A(H1N1) virus and its nearest relatives indicates that its gene segments have been circulating undetected for an extended period. Its low genetic diversity suggests that the introduction into humans was a single event or multiple events of similar viruses. Molecular markers predictive of adaptation to humans are not currently present in 2009 A(H1N1) viruses, suggesting that previously unrecognized molecular determinants could be responsible for the transmission among humans. Antigenically the viruses are homogeneous and similar to North American swine A(H1N1) viruses but distinct from seasonal human A(H1N1).
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Antibodies, Viral / immunology
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Antigens, Viral / genetics
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Antigens, Viral / immunology*
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Disease Outbreaks
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Evolution, Molecular
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Genes, Viral
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Genetic Variation
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Genome, Viral
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Hemagglutination Inhibition Tests
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Hemagglutinin Glycoproteins, Influenza Virus / chemistry
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Hemagglutinin Glycoproteins, Influenza Virus / genetics
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Hemagglutinin Glycoproteins, Influenza Virus / immunology
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Humans
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Influenza A Virus, H1N1 Subtype / classification
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Influenza A Virus, H1N1 Subtype / genetics*
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Influenza A Virus, H1N1 Subtype / immunology*
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Influenza A Virus, H1N1 Subtype / isolation & purification
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Influenza A Virus, H3N2 Subtype / genetics
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Influenza A virus / genetics
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Influenza, Human / epidemiology
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Influenza, Human / immunology
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Influenza, Human / virology*
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Mutation
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Neuraminidase / genetics
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Orthomyxoviridae Infections / veterinary
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Orthomyxoviridae Infections / virology
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Phylogeny
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Reassortant Viruses / genetics
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Swine
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Swine Diseases / virology
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Viral Matrix Proteins / genetics
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Viral Nonstructural Proteins / genetics
Substances
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Antibodies, Viral
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Antigens, Viral
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Hemagglutinin Glycoproteins, Influenza Virus
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NS protein, influenza virus
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Viral Matrix Proteins
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Viral Nonstructural Proteins
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Neuraminidase