Figure 6
From: The evolution of human influenza A viruses from 1999 to 2006: A complete genome study
(A) Seasonal amino acid distances of H3N2 HA and NA proteins since 1999 and (B) amino acid distances of H3N2 HA and NA from one season to the next. The same trends were observed for nucleotide distances. In 2000–2001 H1N1 viruses only were observed and therefore not included. Distance means were computed as the arithmetic mean of all pair wise distances between two seasons in the inter-season comparisons by the MEGA v.3.1 software [68]