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Maximum clade credibility trees for clusters suggesting onward transmission of nonsubtype B strains imported into the United States. Cluster 1 was subsampled into 1A and 1B for phylogenetic inference and display. U.S. sequences with evidence of onward transmission within the United States are indicated with bold branches. Posterior probability support for a given node ≥0.95 is designated with an asterisk. Time in indicated on the x-axis.
