Health officials are warning that small outbreaks of infections spread by contaminated operating room machinery during open-heart surgery could be more widespread than first thought.
The U.S. Centers for Disease Control and Prevention alerted doctors and hospitals on Thursday.
The contamination has been tied to 28 cases in the U.S., including at least four who died — though it's not certain that the bacterial infection caused those deaths. But officials think hundreds or thousands of other patients could also have been infected.
The outbreaks have been tracked to certain heater-cooler devices, which are used to keep patients' hearts cold and bodies warm during some heart operations.
The manufacturer of the devices identified the contamination in its factory in Germany in 2014 and reportedly cleaned it up. But bacteria traced to the machines were linked to clusters of illnesses in Switzerland, Pennsylvania, Iowa and Michigan.
Officials think the Stockert 3T machines, made by London-based LivaNova, are used in roughly half of the 250,000 cardiopulmonary bypass operations performed in the U.S. each year.
They don't think infection occurred in everyone who had a surgery in which that machine was used. The CDC estimates that in hospitals where at least one infection has been identified, the risk of a patient getting an infection from the bacteria was somewhere between 1 in 100 and 1 in 1,000.
There seems to be a higher risk for patients who had valves or other products implanted, health officials said.
Twenty-one Pennsylvania cases were reported by three hospitals — Wellspan York Hospital, Penn State Hershey Hospital and Penn Presbyterian in Philadelphia. Five cases were reported in Iowa, by the University of Iowa and Mercy Medical Center. And two cases in western Michigan were reported by Spectrum Health Medical Center.
The bacteria, Mycobacterium chimaera, is commonly found in soil and water and does not cause illness in most healthy people. But it can be more serious in patients who are in a weakened state after a serious surgery. Even in those patients, however, it can take months for symptoms to develop.
The device was also recalled in Canada.
Patients who have had open heart surgery should seek medical care if they are experiencing symptoms like night sweats, muscle aches, weight loss, fatigue, or unexplained fever, said the CDC's Dr. Michael Bell.
Officials stressed that no one should postpone potentially life-saving heart surgeries because of the contamination concerns.