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Phylogenetic tree of ORF1–ORF7 global representative PRRSV-1 nucleotide sequences. The three vaccine strains are marked with black triangles and the challenge (REC) and reference (REF) strains are marked with grey and black stars, respectively. The tree was constructed with the Neighbor-Joining algorithm and 1000 bootstrap replicates and visualized in FigTree v.1.4.4.
