The Centers for Disease Control and Prevention said 44 cases of infection by the bacteria carbapenem-resistant enterobacteriaceae, or CRE, have been reported, with 38 linked to patients at Advocate Lutheran General Hospital, north of Chicago.
Those infected had all received a fairly routine endoscopic procedure of the pancreas between January and September 2013.
There had only been 96 documented infections of CRE since the bacteria was first discovered in 2009, the Chicago Sun-Times reported. Prior to this outbreak, the largest cluster of reported cases was 10 in the Denver area in 2012.
CRE is a bacteria in the E. coli family that normally lives in the digestive system. Most frequently, it causes urinary tract infections, which if not identified quickly, can enter the bloodstream. If the infection reaches that stage, the patient has a 40 percent to 50 percent chance of death, the CDC said.
Whether any of the 44 cases resulted in fatalities was not reported.
Hospital officials told the Sun-Times all patients who underwent the procedure during the time frame have been sent registered letters asking them to return to the hospital for a screening. More than 100 patients have already done so with more screenings scheduled, the hospital said.
The CDC noted hospital staff followed proper procedures in disinfecting the scopes that tested positive for CRE, which is highly resistant to antibiotics. Since then, the hospital has gone from manual disinfecting to a gas disinfecting, the process generally used for surgical equipment.