Triple reassortant H3N2 influenza A viruses, Canada, 2005

Abstract

Since January 2005, H3N2 influenza viruses have been isolated from pigs and turkeys throughout Canada and from a swine farmer and pigs on the same farm in Ontario. These are human/classical swine/avian reassortants similar to viruses that emerged in US pigs in 1998 but with a distinct human-lineage neuraminidase gene.

Figure 1

Nucleotide phylogram for the hemagglutinin (HA) genes of A/Swine/Manitoba/12707/05, A/Swine/Alberta/14722/05, A/Swine/British Columbia/28103/05, A/Swine/Ontario/33853/05, A/Turkey/Ontario/31232/05, A/Ontario/RV1273/05, and related reference viruses. The evolutionary relationships among these viruses were estimated by the method of maximum parsimony (PAUP software, version 4.0b10) with a bootstrap resampling method (200 replications) and a fast heuristic search algorithm. Numbers at the nodes of the phylograms indicate the bootstrap confidence levels. Horizontal-line distances are proportional to the minimum numbers of nucleotide changes needed to join nodes and gene sequences. Vertical lines are present to space the branches and labels. The designations I, II, and III identify clusters of viruses previously defined among triple reassortant swine viruses in the United States (4). The viruses described in this report and related viruses are proposed to represent a new cluster IV group of viruses. GenBank accession numbers for the sequences of all reference viruses are provided in parentheses after the virus names.

Figure 2

Nucleotide phylogram for the neuraminidase (NA) genes of A/Swine/Manitoba/12707/05, A/Swine/Alberta/14722/05, A/Swine/British Columbia/28103/05, A/Swine/Ontario/33853/05, A/Turkey/Ontario/31232/05, A/Ontario/RV1273/05, and related reference viruses. The evolutionary relationships among these viruses were estimated by the method of maximum parsimony (PAUP software, version 4.0b10) with a bootstrap resampling method (200 replications) and a fast heuristic search algorithm. Numbers at the nodes of the phylograms indicate the bootstrap confidence levels. Horizontal-line distances are proportional to the minimum numbers of nucleotide changes needed to join nodes and gene sequences. Vertical lines are present to space the branches and labels. GenBank accession numbers for the sequences of all reference viruses are provided in parentheses after the virus names.