Figure 1.
Models for the Global Evolution of Influenza Virus
Two phylogenetic hypotheses depicting the evolution of A/H3N2 influenza virus by (A) global migration, in which isolates from adjacent seasons in the northern and southern hemispheres are interspersed topologically, or by (B) reactivation of latent virus, in which isolates from the northern hemisphere give rise, in situ, to isolates that circulate in the same locality the next season, and thus are topologically linked (likewise for southern hemisphere viruses).
Figure 2.
Phylogenetic Relationships of the NA Gene of A/H3N2 Influenza Viruses Sampled from New York State (n = 52), New Zealand (n = 51), Australia (n = 45), and Globally (n = 22) from 1998 to 2005, Estimated Using ML
Viral isolates from New York state are highlighted in orange, isolates from New Zealand in green, isolates from Australia in blue, and global isolates in pink. Light yellow rectangles identify viral clades, with numbers in white boxes giving bootstrap values for key nodes (>70%). To clarify reassortment events, capital letters in blue refer to clades that appear in section I of the tree (denoted in pink) on the phylogeny of the concatenated six non-surface glycoproteins; lowercase letters in red refer to clades contained within section II (denoted in light green); and lowercase roman numerals in dark green refer to clades outside sections I and II. Bootstrap values highlighted in yellow identify nodes that define a cross-hemisphere migration event. The tree is rooted by isolate A/New York/327/1999 from the 1998–1999 season (i.e., the earliest sampled isolate), and all horizontal branch lengths are drawn to a scale of nucleotide substitutions per site.
Figure 3.
Phylogenetic Relationships of the HA Gene of A/H3N2 Influenza Viruses Sampled from New York State (n = 52), New Zealand (n = 51), Australia (n = 45), and Globally (n = 13) from 1998 to 2005, Estimated Using ML
Color scheme, rooting, scale, and symbols are the same as those used in Figure 2.
Figure 4.
Phylogenetic Relationships of the Concatenated Six Non-Surface Glycoprotein Segments of A/H3N2 Influenza Viruses Sampled from New York State (n = 52), New Zealand (n = 51), and Australia (n = 45) from 1998 to 2005, Estimated Using ML
Color scheme, rooting, scale, and symbols are the same as those used in Figure 2.
Table 1.
Clades in the HA, NA, and Concatenated Six Non-Surface Glycoprotein Segment Phylogenies Comprised of Viruses from New York State, New Zealand, Australia, and Globally
Table 2.
Direction of 11 Migration Events between New York State in the Northern Hemisphere and Australia and New Zealand in the Southern Hemisphere