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HA gene phylogeny of influenza B/Victoria-lineage viruses detected in Bulgaria during the 2015/2016 season. Reference viruses are indicated in bold and vaccine virus B/Brisbane/60/2008 in red. Bulgarian viruses detected in January, February and March 2016 are indicated in green, blue and pink, respectively. The tree is rooted at B/Malaysia/2506/2004. Amino acid substitutions defining particular nodes are indicated and bootstrap values > 70% are shown in parentheses.
