A rare and often fatal fungal infection capable of attacking the brain is showing up far more often in the United States than it used to, according to a new report from the Centers for Disease Control and Prevention, which is now calling for better national tracking of the pathogen.
The fungus, Cladophialophora bantiana, is a black, yeast-like mold containing a dark pigment called melanin. Data from a microbiology laboratory at the University of Washington shows detection of the fungus nearly quadrupled between 2023 and 2025.
Between January 2009 and July 2026, researchers identified 48 confirmed cases and one probable case in tissue samples from 21 states and the District of Columbia. The median patient age was 68.
Notably, roughly half of these infections occurred in people without weakened immune systems, a departure from many fungal diseases that typically strike only the immunocompromised. Researchers believe the mold enters the body through inhalation or a skin wound and then travels through the bloodstream to the brain. Of confirmed cases, 88% were detected in brain tissue samples and 12% in lung tissue, consistent with the theory that breathing in the mold is a primary route of infection.
A Low Survival Rate
A systematic review published in Medical Mycology found the infection carries a fatality rate of 60% to 70%, even with aggressive treatment, which typically involves surgery to remove infected tissue along with multiple antifungal medications.
The pathogen was historically rare. The University of Washington laboratory identified only one to five cases a year between 2009 and 2023. That changed sharply in 2024, when annual cases jumped to eight, then to 14 in 2025.
To rule out the possibility that the apparent rise was simply due to increased testing, researchers compared infection counts against the total number of brain tissue samples tested for fungi. They found detections climbed from 8.4 cases per 1,000 specimens during 2017-2023 to 26 cases per 1,000 specimens in 2025.
