Maximum-likelihood (ML) tree of influenza A NA subtypes.

Abstract

<p>A: N1; B: N2; C: N5; D: N8. The annotation for each lineage was labeled on the trees. Three lineages in N1 (1A, 1B and 1C), two lineages in N2 (2A and 2B), two lineages in N5 (5A and 5B), and two lineages in N8 (8A and 8B) were classified. The bootstrap values supporting the corresponding lineages are shown to the left of the major nodes. Scale bars indicate the numbers of nucleotide substitutions per site.</p