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Maximum likelihood trees of segment 1-4 of H3N2 CIVs. (A) PB2; (B) PB1; (C) PA; (D) HA. Colored branches represent distinct lineages. H3N2 CIVs: red, H3N8 CIVs: purple, SIVs: yellow, Eurasian avian lineage: green, and American avian lineage: blue. The bars are drawn to scale.
