A new, more extreme strain of MRSA. MRSA is a bacterial infection highly resistant to antibiotics. USA200 has a high resistance to those antibiotics that still have some effect on the more common MRSA strain.
MRSA is something you used to only find in hospitals. Now the beast is loose, and you are seeing it anywhere there is lots of physical contact - HS football players catching it from artificial turf. Wrestlers in IC and Prep competitions are catching it, etc.
USA200 started cropping up in SF, Mass, NYC and other areas of high homosexual population concentrations. Totally downplayed in the MSM, but the CDC is starting to freak out, because the same sort of epidemiological patterns they saw with AIDS is manifesting with USA200, only way, way faster.