2009 h1 n1 add rd

2009 h1 n1 add rd - Antigenic and Genetic Characteristics...

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/ www.sciencexpress.org / 22 May 2009 / Page 1/ 10.1126/science.1176225 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 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 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). Influenza pandemics occur when an influenza virus with a hemagglutinin (HA), against which there is little or no existing immunity, emerges in the human population and efficiently transmits from human-to-human. The genomes of the last three pandemic influenza viruses (1918 H1N1, 1957 H2N2 and 1968 H3N2) all originated in whole or in part from non-human reservoirs, and the HA genes of all of the pandemic viruses ultimately originated from avian influenza viruses. A(H1N1) influenza viruses were first isolated from swine in 1930 ( 1 ) and have been shown to be antigenically highly similar to a recently reconstructed human 1918 A(H1N1) virus ( 2 ), and likely share a common ancestor ( 3 , 4 ). From 1930 to the late 1990s these "classical swine influenza" viruses circulated in swine and remained relatively antigenically stable ( 5 , 6 ). In, or just before, 1998 the classical swine influenza viruses reassorted with a contemporary human A(H3N2) influenza virus and an American lineage avian influenza virus of an unknown subtype resulting in the emergence of a triple reassortant H3N2 (rH3N2) swine virus in swine populations throughout North America ( 7 9 ). Shortly after the initial detection of the rH3N2 virus, subsequent reassortment between the rH3N2 virus and classical H1N1 swine virus is Antigenic and Genetic Characteristics of Swine-Origin 2009 A(H1N1) Influenza Viruses Circulating in Humans Rebecca J. Garten* 1 , C. Todd Davis* 1 , Colin A. Russell 2,3 , Bo Shu 1 , Stephen Lindstrom 1 , Amanda Balish 1 , Wendy M. Sessions 1 , Xiyan Xu 1 , Eugene Skepner 2 , Varough Deyde 1 , Margaret Okomo-Adhiambo 1 , Larisa Gubareva 1 , John Barnes 1 , Catherine B. Smith 1 , Shannon L. Emery 1 , Michael J. Hillman 1 , Pierre Rivailler 1 , James Smagala 1 , Miranda de Graaf 2,4 , David F. Burke 2 , Ron A. M. Fouchier 4 , Claudia Pappas 1 , Celia M. Alpuche-Aranda 5 , Hugo López-Gatell 5 , Hiram Olivera 5 , Irma López 5 , Christopher A. Myers 6 , Dennis Faix 6 , Patrick J. Blair 6 , Cindy Yu 7 , Kimberly M. Keene 8 , P. David Dotson, Jr.
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2009 h1 n1 add rd - Antigenic and Genetic Characteristics...

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