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J Infect Dis. 2016 Jan 15;213(2):173-82. doi: 10.1093/infdis/jiv399. Epub 2015 Aug 4.

Evolutionary Dynamics of Influenza A Viruses in US Exhibition Swine.

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Fogarty International Center, National Institutes of Health, Bethesda.
J. Craig Venter Institute, Infectious Disease Group, Rockville, Maryland.
Department of Veterinary Biomedical Sciences Department of Veterinary Population Medicine, University of Minnesota, Saint Paul.
US Department of Agriculture National Veterinary Services Laboratories, Ames, Iowa.
Department of Veterinary Preventive Medicine, The Ohio State University, Columbus.


The role of exhibition swine in influenza A virus transmission was recently demonstrated by >300 infections with influenza A(H3N2) variant viruses among individuals who attended agricultural fairs. Through active influenza A virus surveillance in US exhibition swine and whole-genome sequencing of 380 isolates, we demonstrate that exhibition swine are actively involved in the evolution of influenza A viruses, including zoonotic strains. First, frequent introduction of influenza A viruses from commercial swine populations provides new genetic diversity in exhibition pigs each year locally. Second, genomic reassortment between viruses cocirculating in exhibition swine increases viral diversity. Third, viral migration between exhibition swine in neighboring states demonstrates that movements of exhibition pigs contributes to the spread of genetic diversity. The unexpected frequency of viral exchange between commercial and exhibition swine raises questions about the understudied interface between these populations. Overall, the complexity of viral evolution in exhibition swine indicates that novel viruses are likely to continually reemerge, presenting threats to humans.


United States; evolution; exhibition animals; gene flow; genomics; human-animal interface; influenza A virus; swine

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