A rare fungal infection capable of attacking the human brain and killing up to 70% of infected patients is being detected at increasing rates across the U.S,, prompting warnings from federal health officials.
The Centers for Disease Control and Prevention (CDC) has identified a concerning rise in cases involving Cladophialophora bantiana, a darkly pigmented, yeast-like mold capable of causing severe infections in the brain.
According to a new CDC report, laboratory detections of the fungus nearly quadrupled between 2023 and 2025, raising concerns about a pathogen that can affect individuals with otherwise healthy immune systems.
Researchers from the University of Washington analyzed tissue samples collected between January 2009 and July 2026, identifying 48 confirmed infections and one probable case across 21 states and Washington, D.C.
The median age of affected patients was 68.
Unlike many fungal infections that primarily threaten individuals with weakened immune systems, approximately half of C. bantiana infections occur in people without underlying immune deficiencies.
The fungus is believed to enter the body through inhalation or an open wound before potentially traveling through the bloodstream to the brain.
Once there, the infection can produce dangerous abscesses that are difficult to diagnose and treat.
Researchers found that 88% of the identified infections involved brain tissue, while the remaining 12% were detected in lung tissue.
The condition carries a particularly alarming mortality rate.
According to a systematic review published in the medical journal Medical Mycology, between 60% and 70% of patients with the infection die, even when aggressive medical treatment is provided.
Federal researchers are now examining why detections have increased after years of relatively low numbers.
Between 2009 and 2023, the University of Washington microbiology laboratory typically identified just one to five cases annually.
However, that figure climbed to eight in 2024 before reaching 14 in 2025.
To determine whether the increase simply reflected additional testing, researchers compared positive detections against the total number of brain tissue specimens examined for fungal infections.
The results showed that detection rates climbed from 8.4 cases per 1,000 specimens between 2017 and 2023 to 26 per 1,000 specimens in 2025.
“Reasons for the apparent increase are unknown,” the CDC report stated.
The findings also revealed that infections have been identified across a broad geographic area.
California recorded the highest number of cases, with six, followed by Florida and Texas with five each. Pennsylvania reported four.
Health officials are particularly concerned about the challenges involved in identifying the infection before substantial damage occurs.
C. bantiana can develop into a brain abscess without producing obvious external symptoms, making early detection difficult.
In one fatal case documented at the University of Washington Medical Center, spinal fluid tests returned negative results despite the presence of the fungus.
Those negative findings occurred both a month before and at the time of a brain biopsy, demonstrating how conventional testing methods can fail to identify the infection.
Physicians may consequently need to obtain tissue samples through surgical procedures to establish a diagnosis.
Treatment generally involves removing infected tissue and administering multiple antifungal medications.
However, even intensive medical intervention does not guarantee survival.
The CDC is urging medical professionals to consider rare fungal pathogens when evaluating patients with suspected brain abscesses, per Fox News.
Researchers are also calling for systematic nationwide reporting to improve surveillance and determine whether infections are becoming more common across the country.
For now, officials have not identified what is driving the increase in laboratory detections.
The infection remains rare, but its high fatality rate and ability to affect otherwise healthy individuals have raised concerns among researchers investigating its apparent spread.
