U.S. health officials said Thursday they now have evidence of an untreatable fungus spreading in two hospitals and a nursing home.

The "superbug" outbreaks were reported in a Washington, D.C, nursing home and at two Dallas-area hospitals, the Centers for Disease Control and Prevention reported. A handful of the patients had invasive fungal infections that were impervious to all three major classes of medications.

"This is really the first time we've started seeing clustering of resistance" in which patients seemed to be getting the infections from each other, said the CDC's Dr. Meghan Lyman.

The fungus, Candida auris, is a harmful form of yeast that is considered dangerous to hospital and nursing home patients with serious medical problems. It is most deadly when it enters the bloodstream, heart or brain. Outbreaks in health care facilities have been spurred when the fungus spread through patient contact or on contaminated surfaces.

Health officials have sounded alarms for years about the superbug after seeing infections in which commonly used drugs had little effect. In 2019, doctors diagnosed three cases in New York that were also resistant to a class of drugs, called echinocandins, that were considered a last line of defense.

In those cases, there was no evidence the infections had spread from patient to patientscientists concluded the resistance to the drugs formed during treatment.

The new cases did spread, the CDC concluded.

In Washington, D.C., a cluster of 101 C. auris cases at a nursing home dedicated to very sick patients included three that were resistant to all three kinds of antifungal medications. A cluster of 22 in two Dallas-area hospitals included two with that level of resistance. The facilities weren't identified.

Those cases were seen from January to April. Of the five people who were fully resistant to treatment, three diedboth Texas patients and one in Washington.

Lyman said both are ongoing outbreaks and that additional infections have been identified since April. But those added numbers were not reported.

Investigators reviewed medical records and found no evidence of previous antifungal use among the patients in those clusters. Health officials say that means they spread from person to person.

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—Mike Stobbe