Drug-Resistant Fungal Infections Are on the Rise in the U.S.

The nation’s top health officials are sounding the alarm about Candida auris, a deadly, drug-resistant fungus that’s spreading rapidly across the United States.

Since its first detection in the country in 2016, the yeast has now expanded to more than half of U.S. states, Centers for Disease Control and Prevention researchers reported this week in the journal Annals of Internal Medicine. In addition to its growing geographic reach, the fungus is also sickening more people: C. auris infections rose by more than 200 percent—from 476 yearly cases to 1,471—from 2019 to 2021, per the study.

“We’ve seen increases not just in areas of ongoing transmission, but also in new areas,” says study co-author Meghan Lyman, chief medical officer for the CDC’s Mycotic Diseases Branch, to NBC News’ Linda Carroll.

Healthy people typically do not get sick from exposure to C. auris, but the fungus is a big concern for those with compromised immune systems, patients who use invasive medical devices such as breathing or feeding tubes, or people living in long-term care facilities. Once the fungus makes its way into a hospital or senior care center, it’s difficult to eradicate. The yeast survives for a long time on surfaces and can be hard to stamp out with some typical disinfectants. Nurses and doctors can accidentally spread the fungus from person to person as it clings to their clothing, gloves and other personal protective gear.

Once it spreads, C. auris can infect a person’s ears, wounds and bloodstream, according to the CDC. Doctors diagnose C. auris by culturing the patient’s blood or other body fluids, but it can be difficult to differentiate it from other similar types of fungi.

Physicians typically treat these infections with antifungal drugs, but scientists say C. auris is becoming increasingly resistant to such medications.

“The scary thing about C. auris, and any of the drug-resistant fungal infections, is just how difficult it is to find good, safe antifungals,” says Lance B. Price, the co-director of the Antibiotic Resistance Action Center at George Washington University who was not involved in the recent study, to USA Today’s Adrianna Rodriguez.

It’s not clear exactly how many people have died from C. auris, in part because many of the people it infects are already battling severe illnesses that might also shorten their lifespans. But scientists estimate the C. auris mortality rate to be somewhere between 30 and 60 percent, per the CDC.

To understand the current status of C. auris, the researchers compiled and studied local and state health department numbers from 2016 through the end of 2021. They considered patients who became ill because of the fungus as well as those who did not get sick but carried the fungus somewhere on their bodies. Between 2016 and 2021, health officials documented 3,270 total C. auris infections, plus another 7,413 cases where the virus was present on a person but did not cause illness.

Case counts have grown every year since 2016 but increased the most quickly in 2020 and 2021, amid the Covid-19 pandemic. From 2019 to 2021, the fungus also spread geographically: 17 states recorded their first-ever C. auris case.

The study did not include 2022 numbers, however, the CDC says it continued to see a sharp uptick: According to preliminary numbers, health officials recorded 2,377 C. auris infections last year.

Warming global temperatures resulting from human-caused climate change may be to blame for the yeast’s proliferation. With typical temperatures between 97 and 99 degrees Fahrenheit, human bodies have historically been too hot for fungi like C. auris to survive. However, research suggests that as the climate has gotten hotter, C. auris has evolved to persist at warmer temperatures, which has allowed it to flourish among humans.

The Covid-19 pandemic also likely contributed to the rise of this fungal pathogen, reports Matt Richtel for the New York Times. The pandemic shifted medical attention toward the Covid-19 virus and away from testing for C. auris, which may have allowed the fungus to proliferate undetected. In addition, health care providers worked long hours and likely didn’t change their clothing or equipment as often as they typically would. The yeast could also cling to medical equipment used to help treat Covid-19, such as ventilators. In other words, C. auris spread under the general “strain on healthcare and public health systems” throughout the pandemic, per the CDC.

Globally, health officials first detected C. auris in Japan in 2009. Since then, it has been found in more than 30 countries, per the CDC. After conducting genetic sequencing of C. auris from different nations, researchers determined that it likely emerged independently in several regions of the world at the same time. This discovery also supports the idea that climate change contributed to its spread, experts say.

“The most mysterious thing is that Candida auris appeared simultaneously in three different continents, and it’s very hard to explain that,” Arturo Casadevall, a microbiologist at Johns Hopkins University who co-authored a 2019 study linking the fungus to climate change, told the Washington Post’s Lena H. Sun at the time. “You gotta try to think, what could be the unifying cause here? These are different societies, different populations … But the one thing they have in common is that the world is getting warmer.”

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Sarah Kuta is a writer and editor based in Longmont, Colorado. She covers history, science, travel, food and beverage, sustainability, economics and other topics.