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Phylogenetic trees constructed using 20 isolates and the H1 HA (n = 515), H3 HA (n = 184), N1 NA (n = 414), N2 NA (n = 240), MP (n = 460), NS (n = 454), PA (n = 432), PB1 (n = 440), and PB2 (n = 437) gene segments available from GenBank. The 20 new swine influenza virus (IAV-S) isolates are marked with red dots.
