A Drug-Resistant Fungus Is Spreading Through American Hospitals

Spread, or Better Surveillance?

The report counts two kinds of cases. A clinical case is the fungus detected in a patient being worked up for a suspected infection; a screening case is the fungus found by swabbing a patient to check for colonization, the organism living on the skin without causing infection. Because colonization can precede infection, one patient may count as both a screening case and, later, a clinical case, so the two totals overlap and cannot be summed. Both rose steeply between 2022 and 2024.

Whether that rise reflects more frequent infections or more looking is hard to settle. Reported cases are a function of effort as much as of biology: hospitals expanded testing and screening, and screening cases became nationally notifiable in 2023, each of which lifts the count independent of transmission. The CDC is explicit that it cannot apportion the increase among these causes.

One slice of the data resists that ambiguity. Only about a third of clinical cases come from blood; the rest are found in urine, wounds and the respiratory tract, where the fungus is often colonizing rather than invading. A bloodstream infection is unambiguous disease, and it forces the laboratory to name the species, because treatment depends on it. Yeast from urine or sputum is often reported without that precision, and only gradually have labs adopted the methods that distinguish Candida auris from commoner relatives, so those counts climb partly as testing improves. Blood is close to method-proof. Blood cases rose about 60 percent across the two years, from 991 to 1,586, while all clinical cases together more than doubled, so blood’s share fell from a third to a quarter. The faster growth sits in those same non-blood specimens, much of it colonization rather than serious infection. The dependable measure of how much invasive disease has grown is the 60 percent that blood shows, not the headline doubling.

One trend runs the other way. Although the totals keep climbing, the year-over-year increases are shrinking, from 96 percent between 2021 and 2022 to 54 and then 40 percent. The CDC suggests the slowdown may reflect a return to standard infection-control practices as the pandemic’s strains on staffing and supplies eased. Cases still rise every year, but a slowing rate is what one would expect if those defenses were regaining their footing.

What I will be watching is resistance: nearly every isolate already defeats fluconazole, and whether the still-rare strains that also defeat the echinocandins, or every antifungal at once, stay rare will decide how dangerous Candida auris becomes, a question this surveillance cannot answer because it records no susceptibility results.

Screening Moves to the Front Door

Where hospitals look for the fungus has changed over the three years. Screening means swabbing patients to find carriers and isolating them before the organism reaches roommates and equipment. That effort once concentrated in long-term acute care hospitals and ventilator units, where the most vulnerable patients cluster.

In 2022 long-term acute care hospitals accounted for 56 percent of screening detections and ordinary acute care hospitals for 25; by 2024 the proportions had inverted, to 36 and 51. The likeliest explanation is mundane: hospitals began screening at admission, catching patients colonized elsewhere, rather than colonization migrating between facilities.

The patients themselves did not change. Nearly nine in ten are 45 or older and 61 percent are men, the patients with the classic risk factors for colonization: long hospital stays, ventilators, central lines and heavy antibiotic use. The male predominance, consistent across the three years, remains unexplained.

The slowdown the CDC attributes to renewed infection control depends on the unglamorous practices its guidance prescribes: hand hygiene, patient isolation, and disinfection with the few products that kill the fungus. Those defenses gave way during the pandemic, and the fungus surged. Investigations of the outbreaks that followed pinned them on shortages of protective equipment, lapses in hand hygiene and overcrowded units. Whether the increments keep shrinking depends on how well the routines hold now.