If you're tracking emerging infectious agents in the United States, it's time to add a new one to the list.

The Centers for Disease Control and Prevention has identified seven cases of a fungal infection first seen in Japan in 2009. The culprit is called Candida auris.

The fungus has appeared among hospitalized patients with cancer-damaged immune systems or other serious conditions.

Four of the seven patients died. Because they were all quite ill to begin with, it's not clear that the fungus caused their deaths.

"We need to act now to better understand, contain and stop the spread of this drug-resistant fungus," CDC Director Tom Frieden said in a statement. "This is an emerging threat, and we need to protect vulnerable patients and others."

The CDC reported details of these seven cases Friday in an early release of the center's Morbidity and Mortality Weekly Report.

One concern: It appears that in two instances, the fungus may have spread within hospitals. Two cases appeared in an unidentified Illinois hospital. Two cases were also identified in an unidentified New Jersey hospital. These aren't ironclad cases however. In both instances, the patients were on different wards within the same hospital.

The fungus is also hard to identify, though you have to admit that the diagnostic methods sound pretty spiffy. Labs can use "matrix-assisted laser desorption/ionization time-of-flight" analysis, or, if that's not handy, they can sequence the D1-D2 region of the fungus' 28s ribosomal DNA.

The CDC report notes that since the fungus was first identified in Japan seven years ago, it has been detected in Colombia, India, Israel, Kenya, Kuwait, Pakistan, South Africa, South Korea, Venezuela and the United Kingdom.

Many samples of this fungus turn out to be resistant to multiple drugs, though the U.S. cases all responded to at least one antifungal agent.

In June, the CDC asked hospital labs to be on the lookout for this emerging disease. Indeed, five of the seven known cases in the U.S. appeared in 2016.

Copyright 2016 NPR. To see more, visit http://www.npr.org/.