A rare fungal infection that can strike healthy people is rising across the U.S., prompting calls from public health officials for heightened awareness and national tracking.
Cladophialophora bantiana (C. bantiana) is a black yeast-like mold that can infect the brain and contains a dark pigment called melanin, according to a new report from the Centers for Disease Control and Prevention.
Data from a microbiology laboratory at the University of Washington shows that detection of the fungus nearly quadrupled between 2023 and 2025.
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Between January 2009 and July 2026, researchers identified 48 confirmed cases and one probable case of C. bantiana in tissue samples from 21 states and the District of Columbia. The median patient age was 68 years old.
Unlike many fungal infections that mainly affect people with weakened immune systems, about half of C. bantiana infections occur in otherwise healthy people.
Researchers believe the mold enters the body when it is inhaled or through a skin wound, then travels through the bloodstream to the brain.
The CDC report states that 88% of cases were detected in brain tissue samples and 12% were identified in lung tissue, supporting the theory that respiratory inhalation is one of the main transmission mechanisms.
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The fungus causes a severe infection associated with a 60% to 70% fatality rate, even with aggressive medical intervention, according to a systematic review published in Medical Mycology.
The pathogen has historically been rare, with the University of Washington laboratory identifying only one to five cases per year between 2009 and 2023. However, the CDC says annual cases surged to eight in 2024 and reached 14 in 2025.
To make sure the increase wasn’t simply due to more testing, researchers compared the number of infections with the total number of brain tissue samples tested for fungi.
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They found that detections rose from 8.4 cases per 1,000 specimens during 2017–2023 to 26 cases per 1,000 specimens in 2025.
"Reasons for the apparent increase are unknown," the CDC report stated, calling for systematic national reporting mechanisms to better track the pathogen.
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Cases were reported across a wide geographic range, with the highest counts originating in California (six), Florida (five), Texas (five) and Pennsylvania (four).
Because C. bantiana typically manifests as a brain abscess without clear external signs of infection, experts say early diagnosis is challenging.
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In one documented fatal case at the University of Washington Medical Center, spinal fluid PCR tests returned negative results both one month prior to and at the time of a brain biopsy, highlighting the difficulty of detecting the mold.
Public health experts advise clinicians to consider C. bantiana when evaluating patients who have signs of a brain abscess.
Treatment typically involves surgery to remove the infected tissue, along with multiple antifungal medications.