Phylogenetic analysis of the HA1 nucleotide sequences of influenza A(H1N1)pdm09.

<p>Sequences from 81 strains isolated in Thailand between 2010 and 2014 (designated A/Thailand/CU) were compared to the reference strains of known clades reported by WHO Influenza Center London (bolded) and the southern hemisphere vaccine strains recommended by WHO (denoted with triangles). Phylogenic tree was generated using maximum likelihood method by HKY+G model. Bootstrap values of 1,000 replicates >50 are indicated at the nodes. Also at the nodes are the signature amino acid changes in different colors according to epitopes. Scale bar represents approximately 0.2% nucleotide difference between close relatives.