Panel A shows the phylogenetic relationships among pandemic V. cholerae strains on the basis of single- nucleotide variations identified among all strains for which a set of 1588 orthologous genes has been completely sequenced.10 The magnified inset represents strains in the seventh pandemic, including H1, H2, M4, C6, and N5. Panel B shows the phylogenetic relationships among a broad set of seventh-pandemic V. cholerae strains.19 The phylogenetic tree is rooted with three pre-seventh-pandemic strains.