Scientists at the Centers for Disease Control and Prevention (CDC) warned Wednesday that an untreatable, multidrug-resistant "superbug" is spreading in U.S. hospitals and other health care facilities. Fifteen separate strains of Carbapenem-resistant Enterobacteriacea (CRE) were observed in patients in the U.S. in 2012. The bacteria can cause pneumonia, as well as infection in the urinary tract, intestines and the bloodstream.

USA Today reported that species of CRE have infected patients at the National Institute of Health Hospital outside Washington, D.C., killing a 16-year-old boy, as well as at the University of Virginia Hospital, where 7 patients died and thousands of other cases in dozens of hospitals and nursing homes in the U.S. over the last decade. Death rates among CRE-positive patients range from 40 to 50 percent.

Often, physicians don't realize they're dealing with a multidrug-resistant infection until it's too late to save the patient's life. CRE can remain dormant in the system for long periods of time, striking when it finds an opening in the body's immune defenses.

According to Science Daily, CRE can remain in the body up to a year after infection. A study published in the March issue of the American Journal of Infection Control said that patients who tested positive for CRE took, on average, 387 days after hospital discharge to clear their system of the bug. The study, conducted at Shaare Zedek Medical Center in Jerusalem, followed 97 CRE-positive patients who were discharged from the hospital between January 2009 and December of 2010.

Since the first known U.S. case was reported at a North Carolina hospital in 2001, CRE has spread to 41 other states, although in many cases it goes unrecognized because smaller hospitals lack the necessary diagnostic tools to detect it. The lack of clear data about infection rates is frustrating to many clinicians.

Stephen Ostroff, director of epidemiology at the Pennsylvania Department of Health, told USA Today, "We don't have enough … data to tell what the trend looks like. All we know is that it is here."

People who have recently been treated with antibiotics are particularly susceptible to infections by CRE. Currently, there are no drug therapies for infections, and none are currently expected, given that no new antibiotics are currently in production.

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