H1N1 (courtesy AAAS)

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).


Science. ISSN 0036-8075 (print), 1095-9203 (online)
Published Online May 22, 2009
Science DOI: 10.1126/science.1176225

Reports
Submitted on May 12, 2008Accepted on May 22, 2009

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, Bo Shu 1, Stephen Lindstrom 1, Amanda Balish 1, Wendy M. Sessions 1, Xiyan Xu 1, Eugene Skepner 3, 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 4, David F. Burke 3, Ron A. M. Fouchier 5, Claudia Pappas 1, Celia M. Alpuche-Aranda 6, Hugo López-Gatell 6, Hiram Olivera 6, Irma López 6, Christopher A. Myers 7, Dennis Faix 7, Patrick J. Blair 7, Cindy Yu 8, Kimberly M. Keene 9, P. David Dotson Jr.10, David Boxrud 11, Anthony R. Sambol 12, Syed H. Abid 13, Kirsten St. George 14, Tammy Bannerman 15, Amanda L. Moore 16, David J. Stringer 17, Patricia Blevins 18, Gail J. Demmler-Harrison 19, Michele Ginsberg 20, Paula Kriner 21, Steve Waterman 22, Sandra Smole 23, Hugo F. Guevara 24, Edward A. Belongia 25, Patricia A. Clark 26, Sara T. Beatrice 27, Ruben Donis 1, Jacqueline Katz 1, Lyn Finelli 1, Carolyn B. Bridges 1, Michael Shaw 1, Daniel B. Jernigan 1, Timothy M. Uyeki 1, Derek J. Smith 28*, Alexander I. Klimov 1, Nancy J. Cox 1*
1 WHO Collaborating Center for Influenza, Centers for Disease Control and Prevention, USA.2 Department of Zoology, University of Cambridge, UK.; Fogarty International Center, National Institutes of Health, USA.3 Department of Zoology, University of Cambridge, UK.4 Department of Zoology, University of Cambridge, UK.; Department of Virology, Erasmus Medical Center, NL.5 Department of Virology, Erasmus Medical Center, NL.6 Instituto de Diagnóstico y Referencia Epidemiológicos (InDRE) Prolongación de Carpio, México, DF.7 Naval Health Research Center, USA.8 Arizona State Public Health Laboratory, USA.9 Colorado Department of Public Health and Environment, USA.10 Indiana State Department of Health Laboratories.11 Public Health Laboratory, Minnesota Department of Health, USA.12 Nebraska Public Health Laboratory, USA.13 Westchester County Department of Laboratories & Research Public Health Laboratories, USA.14 Wadsworth Center, New York State Dept of Health, USA.15 Ohio Department of Health Laboratory, USA.16 South Carolina Department of Health and Environmental Control, USA.17 Dallas County Health and Human Services, USA.18 San Antonio Metro Health District, USA.19 Diagnostic Virology Laboratory, Texas Children's Hospital, USA.20 San Diego Public Health Laboratory, USA.21 Imperial County Public Health Department, USA.22 CDC Border Infectious Disease Surveillance Project, USA.23 William A Hinton State Laboratory Institute Massachusetts Department of Public Health, USA.24 California Department of Public Health, Viral and Rickettsial Disease Laboratory, USA.25 Marshfield Clinic Research Foundation, USA.26 Michigan Department of Community Health, USA.27 Public Health Laboratory, NYC Department of Health and Mental Hygiene, USA.28 Department of Zoology, University of Cambridge, UK.; Fogarty International Center, National Institutes of Health, USA.; Department of Virology, Erasmus Medical Center, NL.

* To whom correspondence should be addressed.
Derek J. Smith , E-mail: dsmith@zoo.cam.ac.uk
Nancy J. Cox , E-mail: njc1@cdc.gov
These author contributed equally to this work.

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