Phylogenetic analysis of HA gene of the 2009 pandemic influenza A(H1N1) viruses. The HA gene sequences of 10 H1N1pdm Thai isolates, vaccine strain and other viruses retrieved from the NCBI Influenza Virus Resource database were analysed with sequence CY088801 (Thailand-2010/08) as a root of the phylogenetic tree. The GenBank accession numbers, country in which the viruses were detected, and the year and month of detection, are shown. Bootstrap values of more than 50 are indicated on each branch. Circle, strains isolated in this study; triangle, vaccine strain.