Cases of a rare fungus that builds deadly abscesses in the brain have jumped sharply in the United States, and federal health officials still cannot explain the rise.
Researchers counting U.S. infections with Cladophialophora bantiana logged 48 confirmed cases and one probable case from January 2009 through July 2026, the New York Post reported.
Yearly totals stayed between one and five cases from 2009 through 2023. They rose to eight in 2024 and 14 in 2025.
That climb is what triggered the alarm. The same fungus kills up to 70% of the people it infects, can hit patients who are not immunocompromised, and still has no federal tracking system.
Identified infections stretched across 21 states and Washington, D.C. California led with six cases. Florida and Texas each had five. Pennsylvania had four.
Most detections came from brain tissue. Eighty-eight percent of cases were found in brain samples. Twelve percent came from lung samples.
Lab work at the University of Washington showed the same upward line in sharper form. From 2017 to 2023, analysts there found an average of 8.4 cases per 1,000 central-nervous-system specimens submitted for fungal testing. By 2025 the rate was 26 per 1,000, a 210% increase.
Lead author Joshua Lieberman said the published numbers almost certainly understate the real burden.
Lieberman said:
"We think that we’re probably undersampling. We think that that’s probably going to be an underestimate of the true incidence."
About half of those infected did not have the profound immune suppression doctors usually flag as high risk. That pattern is what worries clinicians most.
Lieberman put the problem in plain terms.
He said:
"People who have apparently healthy immune systems get the infection and are also at high risk of death."
He added:
"It’s alarming that it occurs outside of those typical high-risk populations who have pretty profound immunosuppression."
One documented case followed a 44-year-old patient who received surgery and antifungal medication described as optimal treatment. The patient died within three months.
The fungus creates brain abscesses filled with dead tissue and pus. Swelling follows. Vision loss, memory loss, and other neurological damage can come with it. Doctors can mistake the mass for a brain tumor before the lab result lands.
Federal health officials have offered only limited guidance on transmission. The CDC has said relatively little is known about how the organism infects people. Infection is presumed to occur when someone breathes it in or when it enters an open wound.
On the recent spike, the agency’s position is blunt.
The CDC has said:
"reasons for the apparent increase are unknown"
The fungus lives in soil and decaying matter around the world. It was long treated as a tropical problem. Reporting now treats it as present far more widely than that older assumption allowed.
A separate study cited in the coverage found cases also jumped in France in 2022, described there as the warmest year recorded since 1900. Lieberman has pointed to a warming world as one possible factor. Researchers have also mentioned disasters. None of those ideas has been established as the cause of the U.S. rise.
The CDC has warned that the United States has no federal tracking and surveillance program for this infection. Case finding still depends on the labs and clinicians who happen to look for it.
That gap matters once the yearly count moves from a handful of cases to double digits and the death rate stays this high. A pathogen that forms brain abscesses, kills most of the people it infects, and reaches patients with ordinary immune systems is exactly the kind of threat a national system is supposed to catch early.
Instead, the public is left with a retrospective tally, a laboratory rate from one university center, and an official admission that the reasons remain unknown.
Basic disease tracking is core government work. When a fungus this lethal can climb for two years without a federal surveillance system, the failure is already on the record.
