FIG. 1.

Phylogenetic trees based on the sequences of the H6 HA and N1 NA genes of influenza viruses. Nucleotides 29 to 1730 (1,701 bp) of the H6 HA gene were used to construct the HA phylogenetic tree, which was rooted to A/mallard/Potsdam/178-4/83 (H2N2). Nucleotides 66 to 1373 (1,439 bp) of the N1 NA gene were used to construct the NA phylogenetic tree, which was rooted to A/WSN/33 (H1N1). H6 influenza viruses characterized in this study are underlined (NA phylogenetic tree). *, viruses with characteristic deletion of codons for 19 amino acids from the NA gene. The lengths of the horizontal lines are proportional to the minimum number of nucleotide differences required to join nodes. Vertical lines are for spacing branches and labels. Gene sequences used in this study are listed under the following EMBL Nucleotide Sequence Database accession numbers: D90303, X5226, K02252, AF036357, AF057292, AF098548, AF144304, AF098551, and AF208598. Abbreviations: Sh, shearwater; Pa, parrot; Ab, aquatic bird.