A frightening “superbug” has emerged in a major outbreak at U.S. hospitals around the country, and authorities are trying to get a handle on the issue. Candida auris, an often-fatal fungus that is resistant to antibiotics, has started popping up at numerous hospitals, prompting warnings from the Centers for Disease Control and Prevention this week.

This is the first time that the fungus has been found in the United States, and it has killed four of the first seven patients confirmed to have the disease. Dr. Thomas Frieden, the director of the CDC, is urging officials to act now to stop the spread of the disease, calling it an “emerging threat.”

C. auris was first identified in Japan back in 2009, and has since spread to a handful of countries across the world, and it now appears to have found its way to the United States. The first seven cases occurred in New york, Illinois, Maryland and New Jersey in 2013, 2015 and this year.

“Candida auris is an emerging fungus that presents a serious global health threat,” the CDC states on its website. “Healthcare facilities in several countries have reported that C. auris has caused severe illness in hospitalized patients. Some strains of Candida auris are resistant to all three major classes of antifungal drugs. This type of multidrug resistance has not been seen before in other species of Candida. Since 2009, C. auris has been found in patients in several countries, including the United States. CDC expects that as scientists continue to look for this fungus, more cases will be reported in the United States.

“C. auris is difficult to identify with standard laboratory methods and can be misidentified in labs without specific technology. CDC encourages all U.S. laboratory staff who identify C. auris strains to notify their state or local public health authorities and CDC. Find answers to frequently asked questions about C. auris on our questions and answers page and in the Candida auris: Interim Recommendations.”