Multiple Reassortment between Pandemic (H1N1) 2009 and Endemic Influenza Viruses in Pigs, United States
Mariette F. Ducatez, Ben Hause, Evelyn Stigger-Rosser, Daniel Darnell, Cesar Corzo, Kevin Juleen, Randy Simonson, Christy Brockwell-Staats, Adam Rubrum, David Wang, Ashley Webb, Jeri-Carol Crumpton, James Lowe, Marie Gramer, and Richard J. Webby
Author affiliations: Author affiliations: St. Jude Children’s Research Hospital, Memphis, Tennessee, USA (M.F. Ducatez, E. Stigger-Rosser, D. Darnell, C. Brockwell-Staats, A. Rubrum, D. Wang, A. Webb, J.-C. Crumpton, R.J. Webby); Newport Laboratories, Worthington, Minnesota, USA (B. Hause, R. Simonson); University of Minnesota College of Veterinary Medicine, Saint Paul, Minnesota, USA (C. Corzo, K. Juleen, M. Gramer); and Carthage Veterinary Services, Carthage, Illinois, USA (J. Lowe)
Figure 2. Phylogenetic trees of pandemic reassortant swine influenza viruses compared with currently circulating swine influenza strains: A) hemagglutinin (H); B) neuraminidase (N); C) matrix genes. The trees were constructed by using the neighbor-joining method (Kimura 2-parameter) with 1,000 bootstrap replicates. Only bootstrap values >74 are shown. Swine reassortant strains characterized in this study are indicated with a closed circle. Boldface indicates pandemic segments. Greek letters indicate virus genogroups; α represents classical swine influenza virus and δ seasonal human-like swine influenza virus. TR indicates swine triple reassortant influenza virus. Scale bars indicate nucleotide substitutions per site.
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