Fig. 5.

Phylogenetic trees representing the internal genes of influenza A viruses. Trees were constructed based on a 2,302-nt fragment of gene segment 1 (PB2), a 2,285-nt fragment of gene segment 2 (PB1), a 2,151-nt fragment of gene segment 3 (PA), a 1,498-nt fragment of gene segment 5 (NP), a 979-nt fragment of gene segment 7 (MA), and a 885-nt fragment of gene segment 8 (NS). Sequences obtained from influenza virus A/Chicken/Netherlands/1/03 were aligned with those of reference strains available from GenBank, representing the known genetic lineages of influenza A virus. Scale bars represent ≈10% of nucleotide changes between close relatives.