U.S. cases of a deadly fungus nearly doubled in recent years

According to a study by the U.S. Centres for Disease Control and Prevention, a fungus that has recently evolved to infect humans is rapidly spreading in healthcare facilities throughout the United States and becoming increasingly difficult to treat. The Candida auras infections were first identified in the United States in 2013, and since then, the number of infected individuals has risen sharply each year, albeit still small. In 2016, 53 people were affected by the fungus, whereas in 2021, 1,471 people were infected, almost double the 756 cases from the previous year. Furthermore, the researchers have discovered that the fungus is becoming resistant to antifungal medications. The findings have been published in the Annals of Internal Medicine on March 21.

The rise of cases and antifungal resistance is “concerning,” says microbiologist and immunologist Arturo Casadevall, who studies fungal infections. “You worry because [the study] is telling you what could be a harbinger of things to come.” Casadevall, of Johns Hopkins Bloomberg School of Public Health, was not involved in the CDC study.

In tests of people at high risk of infection, researchers also found 4,041 individuals who carried the fungus in 2021 but were not sick at the time. A small percentage of carriers may later get sick from the fungus, says Meaghan Lyman, a medical epidemiologist in the CDC’s Myotic Diseases Branch in Atlanta, possibly developing bloodstream infections that carry a high risk of death.

Starting in 2012, C. auras infections popped up suddenly in hospitals on three continents, probably evolving to grow at human body temperature as a result of climate change (SN: 7/26/19). The fungus, typically detected through blood or urine tests, usually infects people in health care settings such as hospitals, rehabilitation facilities and long-term care homes. Because people who get infected are often already sick, it can be hard to tell whether symptoms such as fevers are from the existing illness or an infection.

According to Lyman, individuals who are ill, have catheters, breathing or feeding tubes, or other invasive medical devices, and those who have repeated or lengthy stays in healthcare facilities are the most susceptible to infection. Although healthy individuals are generally not affected, they can spread the fungus to others through contact with contaminated surfaces, such as gowns and gloves worn by healthcare personnel.

Growing drug resistance

Infections can be treated with antifungal drugs. But Lyman and colleagues found that the fungus is becoming resistant to an important class of such medications called echinocandins. These drugs are used as both the first line and the last line of defence against C. auras, says Casadevall.

Before 2020, six people were known to have echinocandin-resistant infections and four other people had infections resistant to all three class of existing antifungal drugs. That resistance developed during treatment using echinocandin. None of those cases passed the resistant strain to others. But in 2021, 19 people were diagnosed with echinocandin-resistant infections and seven with infections resistant to multiple drugs.

The number of cases of Candida auras recorded each year has been increasing. Clinical cases (dark blue) are among people who had positive urine or blood tests for infections. Screening cases (light blue) are people who carry the fungus, but are not ill at the time of testing. Some screening cases may develop into clinical cases, but others will clear the fungus and have no symptoms. Both carriers and cases may transmit the fungus to others through direct contact with contaminated items.

More concerning, one outbreak in Washington, D.C., and another in Texas suggested people could transmit the drug-resistant infections to each other. “Patients who had never been on echinocandins were getting these resistant strains,” Lyman says.

Some health care facilities have been able to identify cases early and prevent outbreaks. “We’re obviously very concerned,” Lyman says, “but we are encouraged by these facilities that have had success at containing it.” Using those facilities’ infection control measures may help limit cases of C. auras, she says, as well as reducing spread of other fungal, bacterial and viral pathogens.