Figure 1

Neighbor-joining phylograms based on the Kimura 2 parameter genetic distance, showing relationships among infant sequences collected at different time-points, with a set of maternal sequences used for rooting purposes. Infant1449 is a rapid progressor, whereas infant 1984 corresponds to a slow progressor. Maternal sequences are in black in both cases, and branch colors correspond to the time of sample collection. Note that in both cases longer branches correspond mostly to sequences collected at later times. Bootstrap values are indicated at the nodes of the tree.