The United States’ first known case of a superbug that cannot be killed by any existing antibiotic was announced Thursday by the U.S. Department of Defense. Centers for Disease Control and Prevention Director Dr. Tom Frieden announced the case at the National Press Club in Washington.

A 49-year-old Pennsylvania woman developed a carbapenem-resistant Enterobacteriaceae, or CRE, infection. It’s a rare infection but one that Frieden labeled “a nightmare bacteria.” It’s resistant to every known antibiotic, even Colistin, which doctors sometimes use as a last resort when other antibiotics fail. READ MORE