Figure 5.

Characteristics of co-occurring nucleotide modules. (A) Heat map of the distribution of transient and transition modules from 1998 to 2006 subject to hierarchical clustering based on the strain-module profile. Rows correspond to transient and transition modules, and columns correspond to the indicated season. If a transient module is present in a majority of strains in a season, it is blue; otherwise it is gray. Transition modules are labeled according to which of the two member modules is present in the majority of strains in a season (first member, blue; second member, red). (B) Module-based amino acid changes corresponding to the nucleotide changes in transient and transition modules from 1998 to 2006. Each row represents a single amino acid position in a viral protein (labeled on the right). Amino acids (single-letter abbreviations) are also color-coded, so that mutations can be seen as changes both in amino acid identity and color. See Supplemental Figure S3 for all module-based amino acid changes from 1968 to 2006.