A drug-resistant fungus that first emerged in the U.S. only a few years ago has continued to pop up throughout healthcare facilities across the country.

C. auris, a yeast that has sickened people around the globe and is linked to occasionally fatal infections, appears to have arrived in the U.S. around 2013, according to the first report on C. auris released by the CDC back in November.

Between August 2016 and March 2017, the number of C. auris cases rose almost seven-fold, from seven cases to 53, according to a new monthly report from the U.S. Centers for Disease Control and Prevention. That case count doesnt include 27 additional patients whose test results showed the presence of C. auris, but did not have symptoms of an infection.

This jump in cases may be because of spreading infection, or it may be because of better reporting: The CDC asked all U.S. clinics, labs and public health authorities to start collecting information about any potential cases of C. auris in June.

Of the original seven cases that the CDC first reported on in November, four of them died weeks or months after the yeast was identified. All had bloodstream infections of C. auris, but the CDC notes that in general, people with these infections also had serious underlying medical conditions that may have also contributed to their death .