Cases of Candida auris, a drug-resistant and potentially-deadly fungus, nearly doubled in 2021, according to a study by the US Centers for Disease Control and Prevention (CDC). Cases that were resistant to echinocandins, the antifungal medicine that’s most recommended for the infection, have also increased threefold, the CDC found.

In general, Candida auris isn’t a threat to healthy people. Those who are sick, have invasive medical devices, or have long or frequent stays in healthcare facilities are at an increased risk because of their weakened immune systems. The CDC describes it as a global threat due to its resistance to drugs and difficulties to identify it in the lab.

“The rapid rise and geographic spread of cases is concerning and emphasizes the need for continued surveillance, expanded lab capacity, quicker diagnostic tests, and adherence to proven infection prevention and control,” CDC epidemiologist Dr. Meghan Lyman, the lead author of the recent paper, said in a media statement.

A growing risk

Candida auris was first reported in the US in 2016, with a total of 3,270 clinical cases (in which infection is present) and 7,413 screening cases (in which the fungus is detected but not causing infection) reported through December 2021. Cases have also increased every year since 2016, with the most rapid rise happening in the period 2019-2021.

There was a 44% increase in clinical cases in 2019 and then a 95% hike in 2021, the last year with available information. Cases have also expanded geographically. Although initially limited to the New York City and Chicago areas, Candida auris is now present in more than half of the states in the US. 17 states reported their first cases between 2019 and 2021.

It’s likely cases increased because of the coronavirus pandemic, the CDC said, as healthcare and the public health system were under serious strain and may have placed less emphasis on screening. The fungus can attach to gloves, gowns and other personal protective gear, which would have been reused during the pandemic because of a lack of supply.

“Case counts have increased for many reasons, including poor general infection prevention and control practices in healthcare facilities. Case counts may also have increased because of enhanced efforts to detect cases, including increased colonization screening, a test to see if someone has the fungus,” the CDC said.

The spread of Candida auris comes amid growing concerns about health-threatening fungi around the world. The World Health Organization (WHO) published last year its list of “fungal priority pathogens,” including Candida auris. The WHO said fungal pathogens are becoming “increasingly common” and resistant to most treatments.

Waleed Javaid, an epidemiologist and an infectious disease expert, told NBC that the findings are “worrisome” but said it’s unlikely for this to be a problem for healthy people who don’t have medical devices inserted into their blood vessels. The main problem is preventing Candida auris from spreading in the hospital, he added.

The study was published in the journal Annals of Internal Medicine.