Fig. 2.

Amino acid variations between the novel influenza A/H1N1 lineage and their background clade. In the multiple alignment, gap open and gap extension penalties are 15 and 6.66, respectively. Only the variant sites were shown. The background clade represents the closest evolutionary neighbors of the novel A/H1N1 lineage in phylogenetic tree (see Fig. 1). Unique mutation sites exclusively fixed in the novel influenza A/H1N1 lineages are shaded