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. 2013 Jan;77(1):24–32.

Figure 1.

Figure 1

Phylogenetic tree for the hemagglutinin (HA) gene segments, based on nucleotide sequences of swine HA subtype 1 viruses (SwH1) found in the University of Minnesota Veterinary Diagnostic Laboratory and GenBank databases (GenBank accession numbers, when available, in parenthesis), along with the sequences of the challenge virus before and after inoculation (white diamonds) and the 2 H1N1 vaccine viruses (white circle and white triangle). The 4 clusters are SwH1γ (H1N2-like; black circles), SwH1β (reassortant H1N1-like; black squares), SwH1α (cH1N1 or classic-like; black diamonds), and SwH1δ (human-like H1; black triangles). There were 875 nucleotide positions in the final dataset. Bootstrap test results for similarity (500 replicates) are shown next to the branches.