FIG. 5.

Estimated times of divergence of major iVDPV lineages based upon the rate of substitution at third-codon positions within the P1/capsid region interval of nucleotides 743 to 2658. Genetic distances and standard errors were scaled under the single rate dated tips model (68) to the time of specimen collection (time zero: date of last OPV dose) as described in Materials and Methods. Note that isolates are identified by the day of specimen collection, not by the day after the last OPV dose.