One strength of this study is that it shows not only healthcare-associated but also community S. aureus disease to be declining, a decline that is difficult to attribute to hospital-focused interventions. The reports now from NHSN, the Active Bacterial Core Surveillance program, the United Kingdom, the EARSS system, and now the military all speak to our ignorance of the complex interplay between S. aureus and its human reservoir. Successive long cycles of waxing and waning epidemic spread have been, and will be, the rule.
For a nice example, check out this study from Oxfordshire hospitals demonstrating how their MRSA incidence began to drop well in advance of intensified infection control interventions, and how this drop coincided with the rise and fall of two competing strain types.
Image from Planet Science