Researchers at Emory University School of Medicine in Atlanta say the superbugs are spreading outside hospitals.
MRSA infections can range from boils to more severe infections of the blood, lungs and surgery sites.
Most of the cases so far have involved hospitals and nursing homes, but researchers are seeing more infections in the general public.
The infections can be treated only with expensive antibiotics. Researchers say more pneumonia cases are likely and they'd expect mortality rates of more than 50-percent.