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. Author manuscript; available in PMC: 2010 Jan 5.
Published in final edited form as: Virology. 2008 Nov 8;383(1):156–161. doi: 10.1016/j.virol.2008.10.015

Fig. 2.

Fig. 2

Maximum likelihood trees of North American AIVs based on the representative (a) PB2 segment (n = 290) and (b) HA (n = 281) segments. Taxa and terminal branches are colored by sample location. Colored blocks represent the clusters in which samples come from the same location within a certain range of time. The tree is mid-point rooted (for purposes of clarity only) and all horizontal branch lengths have been drawn to a scale of nucleotide substitutions per site.