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The proportions of charge+ (red bar), charge− (green bar), and charge± (black bar) substitutions in HA1 on the trunk, interior, and exterior branches of the NGS+, NGS−, and NGS± branches are indicated for (A) A/H3N2 and (B) A/H1N1 viruses. The number of amino acid substitutions in HA1 is shown in Table S1.
