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Four subclades characterized the evolution of HPAI H5N1 in wild birds and poultry during this period (a) 2.2.1, (b) 2.2.2, (c) 2.2.3 and (d) 2.3.2. The hypothesized mode of virus movement includes; wild birds (yellow), poultry (black) or inconclusive (dashed).
