A lethal, hard-to-treat fungal infection is spreading across the U.S. and becoming increasingly resistant to the few drugs available to treat it, CDC researchers warned on Monday, part of a growing group of deadly microorganisms that pose a pressing but underappreciated health threat worldwide.
Cases of Candida auris, an invasive yeast infection first discovered in Japan in 2009, have risen drastically over the past few years, according to an analysis of national surveillance data published Monday in the Annals of Internal Medicine.
There were 1,471 cases of C. auris reported in 2021, the researchers said, a “dramatic” 95% increase from the year before.
The figure is part of a years-long uptick in C. auris infections, with data showing 756 cases in 2020, 476 in 2019, 330 in 2018 and 173 in 2017.
As the deadly yeast is relatively harmless to most people in good health and can survive on skin or in the environment, experts often screen symptomless patients to prevent it spreading to those at risk of an invasive infection, for example in hospitals and care facilities.
Screening cases—those found to carry the fungus but who do not have symptoms of an active infection—have also increased, the researchers said, with the 4,042 reported in 2021 nearly triple the 1310 in 2020, though part of this could stem from increased testing efforts.
Surveillance data, which showed evidence of increased transmission in the U.S., also indicated a worrying increase in cases resistant to antifungal drugs, particularly a group called echinocandins, which are used as a first-line therapy.
What To Watch For
The researchers said the uptick in fungal infections can partially be explained by the Covid-19 pandemic, which strained already struggling healthcare systems and may have led to lapses in normally effective infection control measures. Some C. auris cases can definitely be linked to the equipment-saving strategy of seeing multiple patients without changing gowns or gloves, Dr. Meghan Lyman, a medical officer in the CDC’s mycotic diseases branch and one of the study’s authors, told Forbes. Strengthening infection control measures—such as practicing good hand hygiene, isolating patients and thoroughly cleaning the environment (C. auris can survive for weeks on surfaces)—and making sure the pathogen is detected as early as possible will help keep cases and transmission down, Lyman said.
Lyman told Forbes the uptick in C. auris cases, as well as evidence of local transmission, is obviously undesirable but stressed it is “not inevitable” that the fungus will keep spreading. Facilities, even those with large outbreaks, have managed to contain the infection before, Lyman said. “I don’t know that we’ll ever eradicate it [or get to the point that it’s] nowhere or there are no transmission events, but we can get to the point of trying to mitigate transmission as much as possible,” Lyman said.
The latest CDC data tracking C. auris cases, which was not analyzed in the study, reported 2,377 clinical cases during 2022, more than a 60% increase from the year before. More than 5,750 screening cases were also reported. Most, if not all, transmission in the U.S. is linked to health care, especially long term facilities. Almost all cases are also now the result of local transmission, a stark difference to most early U.S. cases which were often linked to receiving healthcare abroad.
What We Don’t Know
Neither the study nor the CDC tracker outline the numbers dying from C. auris infections. They are difficult to treat, especially as some strains are resistant to key medicines used to treat the infections. The CDC estimates between 30% and 60% of people with C. auris infections die, though they note this is from a limited number of patients and that many had other serious illnesses that also increased their risk of death.
Fungal infections claim approximately 1.5 million lives each year. The toll puts fungal killers on par with tuberculosis and is more than double that of well-known threats like malaria, HIV and breast cancer. Fungal infections are also a major source of ill-health and disability worldwide. Despite this, they have languished in relative obscurity, are relatively unknown by the public and are largely neglected by health officials and funding agencies. Some, such as the World Health Organization, are now pushing to change this narrative. The WHO outlined a list of “priority pathogens” in an effort to draw more attention to what it calls a “major threat to public health” that is “becoming increasingly common” (the agency classed C. auris as one of four posing the biggest threat to humanity). The highly invasive infections caused by the likes of C. auris are rare and only strike those who are already very unwell and are incredibly difficult to treat. Increasingly, they are exhibiting resistance to what few antifungal drugs we have at our disposal—there are only four classes of antifungal used in medicine—making them even harder to treat.
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