Deadly, brain-liquifying fungus is on the rise in the US — and scientists don’t know why

A rare fungus found around the world kills up to 70% of the people it infects by liquifying the brain.

Now, the CDC is sounding the alarm that cases of this infection have jumped four-fold in just two years.

They warn there’s no federal tracking and surveillance of the disease. Experts are also unsure of how it spreads — and are still in the dark about why cases are steadily rising.

Cladophialophora Bantiana is a dark or black mold and found in soil and decaying matter around the world.

“Relatively little is known” about how the fungus infects humans, the CDC says, though it’s “presumed” to infect people who simply breathe it in, or it gets into an open wound.

Usually, the fungus heads for the brain, where it creates abscesses of dead tissue and pus, causing swelling and neurological issues like vision and memory loss.

Rising cases

The CDC reports that between January 2009 and July 2026, researchers identified 48 confirmed cases (and one probable case) of C. Bantiana infections in the US.

While the number of cases ranged from one to five per year between 2009 to 2023, they rose to eight in 2024 — then jumped to 14 in 2025.

“We think that we’re probably undersampling. We think that that’s probably going to be an underestimate of the true incidence.”

Joshua Lieberman

Most cases (88%) were detected from samples from the brain, though 12% were found from lung samples.

C. Bantiana cases were found in 21 U.S. states and D.C., with the most in California (six cases), Florida (five), Texas (five), and Pennsylvania (four).

From 2017 to 2023, an average of 8.4 cases were detected per 1,000 CNS specimens submitted for fungal analysis at University of Washington. But by 2025, the number increased 210%, to 26 per 1,000.

At least one other fungal lab has seen a rise in the deadly mold, lead author Joshua Lieberman told MedPage Today.

“We think that we’re probably undersampling,” he added. “We think that that’s probably going to be an underestimate of the true incidence.”

Who gets sick?

Those who are immunocompromised are usually at increased risk of black mold infections like this one. However, data shows that the C. Bantiana fungus isn’t picky — about half of those who were infected were not immunocompromised.

“People who have apparently healthy immune systems get the infection and are also at high risk of death,” Lieberman said. “It’s alarming that it occurs outside of those typical high-risk populations who have pretty profound immunosuppression.”

It’s also hard to treat. By the time people realize something’s wrong, it can be misdiagnosed as a brain tumor — and even if they do identify it as a fungal infection, aggressive treatment doesn’t always work.

A 44-year-old who caught the fungus, for example, got “optimal treatment,” including surgery and anti-fungal medication, but still died within three months.

While the CDC says “reasons for the apparent increase are unknown,” Lieberman points to one possibility: a warming world.

Researchers have been warning that warmer temperatures allow for more fungal pathogens to thrive, while others are adapting to environments that they previously couldn’t tolerate. Plus, with more natural disasters, they expect more fungal outbreaks.

C. Bantiana has been thought of in the past as a tropical infection associated with warmer climates and high average humidity — but is now acknowledged to be found worldwide. One study showed that C. Bantiana cases similarly jumped in France in 2022, the warmest year recorded since 1900.