The Centers for Disease Control is warning hospitals about a strain of antibiotic resistant bacteria that has killed up to half the patients that it infects.

Carbapenem-Resistant Enterobacteriaceae (CRE) has developed a resistance to what doctors call “last resort antibiotics.” The resistance could result in patients suffering from an incurable infection.

The CDC said that most CRE infection occur to those in long-term acute care facilities, significant medical care situations in hospitals and nursing homes.

CDC Director Tom Frieden, M.D., called CRE “nightmare bacteria.”

The CDC says almost 200 hospitals and long-term care facilities have had at least one patient with a CRE. The percentage of CRE has increased four times over the last 10 years and that one form of pneumonia has increased seven times.

“Doctors, hospital leaders, and public health, must work together now to implement CDC’s “detect and protect” strategy and stop these infections from spreading,” Dr. Frieden said.