Fig. 2

Fold changes in nucleotide composition between the epidemic start and the last month of analysis. A bar plot shows the fold change in composition of each mono- or oligonucleotide; this value was calculated by dividing the nucleotide composition in the last month of analysis by that at the start of the epidemic. Each bar is colored to indicate the clade, as described in Fig. 1. Since we analyzed strains belonging to different clades separately, data from the first or last month differed among clades; see also the Methods section