Health experts are sounding the alarm over rising cases of a rare but deadly fungus that could liquefy parts of the brain.
In a new study, researchers at the University of Washington and the Centers for Disease Control and Prevention (CDC) found that cases of Cladophialophora bantiana (C. bantiana), a highly dangerous mold that kills 60 to 70 percent of patients, had surged four-fold in just two years.
Between 2009 and 2023, their lab, a major reference lab, detected between one and five cases of the fungus every year. But in 2024, that number rose to eight cases, and in 2025, to 14.
In total, there were 48 confirmed cases of C. bantiana between January 2009 and July 2026 in the US. Scientists fear, however, that there were other infections that were missed.
Reasons ‘for the apparent increase are unknown,’ the researchers wrote in a new CDC report, though they suspect climate change could be to blame.
Cases were found in 21 states and Washington DC, with the highest total, six, reported in California in that timeframe.
Dr Joshua Lieberman, lead study author from University of Washington School of Medicine, said: ‘It’s alarming that it occurs outside of those typical high-risk populations who have pretty profound immunosuppression.
‘People who have apparently healthy immune systems get the infection and are also at high risk of death.’
Health experts are sounding the alarm about a deadly fungus that causes dangerous abscesses in the brain that can mimic tumors and strokes
Lieberman said he published the paper to sound the alarm over rising cases.
He said: ‘We think that we’re probably under-sampling. We think that that’s probably going to be an underestimate of the true incidence.’
The CDC says that ‘relatively little is known’ about how C. bantiana infects humans, though it is ‘presumed’ to infect people who breathe it in from soil, particularly in subtropical or humid regions.
They wrote in the October 2 CDC Morbidity and Mortality Weekly Report: ‘C. bantiana has only rarely been isolated from environmental sources, and many patients do not have similar exposure histories or risk factors.
‘National surveillance does not exist, and neither the environmental reservoir nor the route of infection is fully understood.’
Of the 48 identified cases from 2009 to 2026, as well as one presumed case, 88 percent were found in brain tissue while 12 percent were detected in the lung.
The average patient age was 68.
From 2017 to 2023, on average, 8.4 cases were detected among 1,000 samples from patients’ central nervous systems. By 2025, that number spiked to 26 per 1,000, a 210 percent increase.
California reported six cases, Florida had five, Texas identified five and Pennsylvania reported four. Case totals for the remaining 18 states and territories were not included in the report.
Lieberman told MedPage Today that at least one other fungal lab has seen a rise in C. bantiana.
Along with the US, cases have been identified in Canada, the UK, Japan, India, France, Belgium, South Africa, Mexico, Brazil and Malaysia.
Once the fungus enters the body, it typically travels to the brain. Experts believe it produces melanin, a pigment that influences skin, hair and eye color, which protects it and helps it cross the blood-brain barrier.
The above chart from the CDC’s Morbidity and Mortality Weekly Report shows the gradual increase in infections from Cladophialophora bantiana
When it reaches the brain, it causes the fungal infection phaeohyphomycosis, a severe disease that forms abscesses filled with pus and dead tissue inside the brain. These trigger inflammation and pressure inside the skull, leading to severe headaches, nausea and vomiting.
On brain scans, the abscesses can appear similar to tumors and strokes, which can lead to delayed or misdiagnosis.
People who are immunocompromised are typically at an increased risk of mold infections, but the report shows only about half of those infected had weak immune systems.
Even with aggressive treatments such as surgery to remove lesions and drain abscesses, the mortality rate ranges from 60 to 70 percent.
The authors urged doctors to be aware of the rising cases and signs and symptoms of brain abscesses.
