Parallel Epidemics of Community-Associated Methicillin-Resistant<i>Staphylococcus aureus</i>USA300 Infection in North and South America

Our results reveal the existence of 2 parallel USA300 epidemics that shared a recent common ancestor. The simultaneous rapid dissemination of these 2 epidemic clades suggests the presence of shared, potentially convergent adaptations that enhance fitness and ability to spread.