Why Deadly Candida Auris Fungus Is Spreading So Fast Across the U.S.

In something seemingly out of an episode of The Last of Us, a dangerous fungal infection has been creeping its tendrils across the country.

The U.S. Centers for Disease Control and Prevention announced in a new study published in the journal Annals of Internal Medicine that the fungus Candida auris is spreading increasingly across the United States, with 17 states identifying their first C. auris case between 2019 to 2021.

There was a 44 percent increase in cases seen between 2018 and 2019, which spiked to a 95 percent increase in cases between 2020 and 2021—from 756 cases in 2020 to 1,471 cases in 2021. In 2022, it is believed that there have been 2,377 cases of infection in the United States.

This fungal infection is also resistant to a number of antifungal drugs, and therefore poses a "serious global health threat," according to the CDC.

Candida auris is a yeast that usually causes no symptoms but can lead to blood infections, wound infections, and ear infections in patients with weakened immune systems and those with lines and tubes that go into their bodies.

Those most at risk include immunocompromised people, those who have recently undergone surgery, and those who have some form of diabetes or have recently used broad-spectrum antibiotics and antifungals. The infection most commonly affects people in hospitals, leading to about one in four infected patients dying.

"Infections by C. auris, sometimes called fungemia, have been reported in 30 or more countries, including the United States," Rodney Rohde, a regents' professor of clinical laboratory science at Texas State University, told Newsweek. "They are often found in the blood, urine, sputum, ear discharge, cerebrospinal fluid and soft tissue, and occur in people of all ages.

"According to the U.S. Centers for Disease Control, the mortality rate in the U.S. has been reported to be between 30 to 60 percent in many patients who had other serious illnesses," he said. "In a 2018 overview of research to date about the global spread of the fungus, researchers estimated mortality rates of 30 to 70 percent in C. auris outbreaks among critically ill patients in intensive care."

The reasons for the spike in cases in the U.S. is likely due to transmission in a hospital setting, and the difficulty in detecting this kind of infection.

"C. auris gets shed out in the hospital environment and can persist on patients and equipment," Daniel Henk, a fungi specialist and lecturer in microbial ecology at the University of Bath in England, told Newsweek. "I think an outbreak in a U.K. setting was linked to reusable underarm thermometers. That onward transmission is the biggest thing that stands out about C. auris to me and probably to most other mycologists."

Environmental surfaces and medical devices are common ways for infection to be spread, especially to people with weaker immune systems.

"One of the key mechanisms for this to occur is the formation of biofilms," Rohde said. "Overall, poor general infection prevention and control (IPC) practices in healthcare facilities can be a part of the equation.

"It's possible that during the COVID-19 pandemic, IPC practices took on less importance, especially in the environmental surface aspect, than during non-pandemic times. Another reason could be increased surveillance/testing of individuals who have been detected as colonized but not infected with C. auris."

C. auris was discovered around a decade ago and has only recently started spreading around the world

"It wasn't really known about until about 10 years ago (it was first described in 2009 but didn't get much attention until after 2013. The earliest infection reports are more like, 'hey there's this new fungus causing some infections, and we don't know if it's really bad or not,'" Henk said. "So, unlike the yeasts that have been living with us for a long time and causing all sorts of illness that we are familiar with, C. auris is new for hospitals and clinics and for mycologists too."

Other types of yeast infections are often due to other Candida species, notably Candida albicans, which cause mouth, skin and vaginal infections.

The major concerns that the CDC has included are that C. auris often occurs in a healthcare setting with already weak hospitalized patients, and is often misidentified as another condition due to the difficulty in detection. Additionally, the fungus is often resistant to antifungal drugs, with nearly all samples tested of C. auris having been found to be resistant to at least one class of antifungal drug.

"Even more alarming was a tripling in 2021 of the number of cases that were resistant to echinocandins, the antifungal medicine most recommended for treatment of C. auris infections," Rohde said. "CDC has deemed C. auris as an urgent antimicrobial resistant [AMR] threat, because it is often resistant to multiple antifungal drugs, spreads easily in healthcare facilities, and can cause severe infections with high death rates."

As well as spiking cases in the U.S., the number of cases has also spread across 30 countries.

"The global spread is still early enough that mycologists have kind of been able to identify lineages as they move around, sort of like in SARS-Cov-2," Henk said. "I'm most familiar with the U.K. where there have definitely been increasing outbreaks since it was first reported. Of course, when something is new, it's hard to go any direction but up. So far they have mostly been contained here, but it's a matter of time."

So, what can we do to stop the spread of this strange, deadly fungal infection?

"Everyone should use proper hand hygiene via soap and warm water or alcohol-based hand sanitizers," Rohde said. "Healthcare professionals and similar caregivers should also utilize proper PPE like gloves and gowns. There is also an urgent need for strong diagnostics for accurate identification in the medical and public health laboratory, laboratory stewardship, antimicrobial stewardship, real-time AMR surveillance, and support for antifungal discovery alongside antibiotic and other antimicrobial drug classes."

Preventing transmission in and between hospitals will likely need multiple things in place, Henk explained.

"Probably the most important thing is really improved diagnostics and monitoring that can alert staff early to potential outbreaks," Henk said. "The lack of awareness and regularised monitoring means that once people notice, it's often too late to manage effectively."

It's possible that the effects of climate change may further increase the spread of this fungus over the coming years.

"Some researchers have estimated that climate change and other similar factors [encroachment into non-human habitat] may be leading to increases globally. C. auris as an urgent threat in the United States, or the WHO fungal priority pathogen list that identifies C. auris as a priority globally," Rohde said.

This isn't the only fungal disease that may be being made worse by climate change: frogs around the world are being wiped out by a fungal skin infection known as chytridiomycosis, which may be more effective at spreading due to climate change. Additionally, the human fungal disease "Valley fever," usually only contracted in the southwestern U.S. states, has spread across the country, a shift that is thought to have occurred due to climate change-triggered weather pattern alterations.

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