Although the bacteria, known as Carbapenen-Resistant Enterobacteriaceae, or CRE, haven’t spread to the wider community — like some other germs — they are more dangerous, said Frieden, who described them as a “triple threat.”

First, the bacteria are resistant to all or nearly all antibiotics, even those of last resort, he said. Second, they kill up to half of patients who get bloodstream infections from them. And third, the bacteria can transfer their antibiotic resistance to other bacteria within the family, potentially making other bacteria untreatable, as well.

For example, carbapenem-resistant Klebsiella, which caused the NIH outbreak, “can spread the genes that destroy our last antibiotics to other bacteria, such as E. coli, and make E. coli resistant to antibiotics also,” Frieden said.