CDC Warns on Rise in Deadly Fungal Infections That Spread to the Brain

Detected cases of a rare but deadly fungal infection increased about fourfold from 2023 to 2025 at a U.S. laboratory that tests samples nationwide, and the reasons why aren’t clear, researchers said.

The clinical reference laboratory at the University of Washington identified 48 confirmed cases and one probable case of Cladophialophora bantiana infection from January 2009 to July 2026. While the annual case count ranged from one to five in 2009-2023, it jumped to eight in 2024 and 14 in 2025.

Among the cases, 88% were detected in intracranial central nervous system (CNS) tissue specimens, and 12% were detected in lung specimens, which points to a presumed respiratory infection route, reported Joshua Lieberman, MD, PhD, of the University of Washington School of Medicine in Seattle, and colleagues in the Morbidity and Mortality Weekly Report.

The C. bantiana case rate more than tripled from an annual average of 8.4 cases detected per 1,000 CNS specimens in 2017-2023 to 26 cases per 1,000 specimens in 2025.

Most C. bantiana infections target the CNS and typically present as brain abscesses. “The presumed route of infection is inhalation or direct inoculation after cutaneous injury,” according to the researchers.

The fungal infection is linked to case-fatality rates of up to 70%.

“C. bantiana is a rare but important cause of brain abscess in both healthy and immunosuppressed people,” Lieberman told MedPage Today. Where people get it from and why it primarily goes to the brain “remain a little bit of a mystery,” he noted.

What sets these infections apart “is that people who have apparently healthy immune systems get the infection and are also at high risk of death,” he said. “It’s alarming that it occurs outside of those typical high-risk populations who have pretty profound immunosuppression.”

Given their rarity, the true incidence of C. bantiana infections isn’t clear, Lieberman pointed out. The rise in detected cases could simply be a product of more submitted specimens and better detection through molecular testing, but “the other reasons that really jump to mind are a warming world and climate change,” he added.

A warming environment puts people at greater risk of fungal infections, Lieberman explained. Evidence also suggests that a number of fungal pathogens are adapting to higher temperatures, making them better able to cause infections. In addition, human encroachment on the environment reservoir of C. bantiana could boost infection risk.

At least one other U.S. specialized fungal lab has seen a rise in detected C. bantiana cases, Lieberman said. Given the difficulty of getting molds to grow in labs, “we think that we’re probably undersampling,” he cautioned. “We think that that’s probably going to be an underestimate of the true incidence.”

For clinicians dealing with a brain abscess who can’t get a diagnosis through cerebrospinal fluid or routine culture — particularly in otherwise apparently healthy people — “I think that’s when you start thinking about rare causes” like C. bantiana, Lieberman suggested. With C. bantiana infections, surgical excision of the abscesses should be paired with combination antifungal therapy with liposomal amphotericin B, posaconazole or voriconazole, and flucytosine.

Among the 49 confirmed and probable cases, median patient age was 68 years. Cases were evenly distributed across the U.S., with detection in samples from 21 states and the District of Columbia. California had the largest number of cases, with six, followed by Florida (five), Texas (five), and Pennsylvania (four).