An Oregon hospital is reporting an outbreak of a superbug fungus that has hospitalized three people in the state, health officials said.

Oregon on Tuesday confirmed three cases of Candida auris at a hospital in Salem, the state capital. The first case was detected on Dec. 11, according to the Oregon Health Authority. The second case was confirmed on Dec. 23 and the third Dec. 27.

Federal, state and local health officials are investigating the outbreak.

C. auris is a type of yeast fungus that is difficult to detect and is heavily resistant to drugs, making treatment of infected patients difficult. The pathogen was first detected in 2009 at a hospital in Japan and inside the U.S. in 2013.

The Centers for Disease Control and Prevention called C. auris a “serious global health threat” and has reported 1,156 clinical cases of the yeast fungus in states stretching from New York to California.

Rebecca Pierce, the manager for the Healthcare-Associated Infections Program in Oregon’s health department, said the fungus “can cause serious infections, particularly in those with serious medical problems.”

“Fortunately, the organism we’re dealing with in this outbreak appears to respond to existing treatments,” she said in a statement. “Nonetheless, it’s critical that we prevent the spread of the infection.”

The fungus can cause bloodstream and wound infections, with symptoms including fever and chills. It can also colonize people’s skin and spread through close contact or via contaminated surfaces.

C. auris is extremely hard to detect and requires special equipment to identify.