Fig 6. A small subset of within-host variants are enriched on spillover branches.

(a) A schematic for how we classified host transitions along the phylogeny. Branches within monophyletic human clades were labelled “to-human” (red branches). Branches leading to a monophyletic human clade, whose parent node had avian children were also labelled as “to-human” (half red, half blue branches), and all other branches were labelled “to-avian” (blue branches). (b) Each amino acid-changing SNV we detected within-host in either ducks (left) or humans (right) that was present in the H5N1 phylogeny is displayed. Each bar represents an amino acid mutation, and its height represents the number of to-avian (blue) or to-human (red) transitions in which this mutation was present along the H5N1 phylogeny. Significance was assessed with a Fisher’s exact test. * indicates p < 0.05, **** indicates p < 0.0001.