FIG 7.

“Dynamic” versus “sedentary” transmission strategies of GAS strains differing in capsule production. Dynamic capsule-positive GAS strains (red) have evolved to transmit in large numbers to naive hosts in a short period of time (B) rather than persisting in the nasopharynx of the colonized host (C). Sedentary capsule-negative GAS strains (blue) transmit at lower titers over a longer period of time (B) and are more likely to persist in contact hosts (C). Differences in GAS transmission burdens observed at a low density of infected individuals (e.g., 1:2) (top right) and a high density of infected individuals (e.g., 1:1) (bottom right) are shown. Each transmission strategy involves contrasting phenotypes of enhanced (green arrows) or reduced (orange arrows) resistance to immune clearance, adherence to epithelia, shedding titers, and colonization persistence.