Conceptual representation of how the TMRCA relates to transmission. Two patients A and B are shown, and a transmission event happened from A to B as indicated by a red arrow. Within each patient, a colonizing population evolves between the time of infection and the time when the patient becomes symptomatic, at which point a single strain is isolated, represented by a red dot. The most recent common ancestor of the two isolates from A and B is shown as a blue dot.
Didelot et al. Genome Biology 2012 13:R118 doi:10.1186/gb-2012-13-12-r118