US researchers and the CDC report a sharp rise in cases of *Cladophialophora bantiana*, a black yeast-like mold that invades brain tissue and forms abscesses.

Between January 2009 and July 2026, 48 confirmed cases and one probable case were identified in tissue samples from 21 states and Washington, D.C., according to the CDC's Morbidity and Mortality Weekly Report.

Annual detections climbed from roughly one to five per year through 2023 to eight in 2024 and 14 in 2025.

Detection adjusted for testing volume rose from 8.4 cases per 1,000 central nervous system specimens during 2017–2023 to 26 per 1,000 in 2025, and researchers said increased testing alone could not account for the change.

Unlike most dangerous fungal infections, which target people with weakened immune systems, about half of documented *C. bantiana* cases occurred in otherwise healthy individuals.

"People who have apparently healthy immune systems get the infection and are also at high risk of death," lead author Joshua Lieberman said, per New York Post reporting.

New York Post notes Lieberman suggested climate warming as one possible driver, pointing to a similar jump in France in 2022, the warmest year recorded since 1900, though the CDC itself says the reasons for the increase are unknown.

Of the 49 specimens, 88% came from brain or central nervous system tissue and 12% from lung tissue — a split supporting the theory that the mold is inhaled through the respiratory tract or enters through skin wounds and travels through the bloodstream. Median patient age was 68.

Cases were geographically widespread, with the most in California (six), followed by Florida and Texas (five each) and Pennsylvania (four). "We think that we're probably undersampling," Lieberman told the press, warning the true incidence is likely higher than reported.

*C. bantiana* typically manifests as a brain abscess with no external signs, and its lesions on brain imaging can resemble tumors or other infections, making early diagnosis extremely difficult.

Standard tests like spinal taps can miss the fungus: Fox News reports that in one fatal case at the University of Washington Medical Center, spinal fluid PCR tests were negative both a month before and at the time of a brain biopsy.

Symptoms can include headaches, dizziness, nausea, vomiting, limb weakness, speech impairment and altered consciousness.

Treatment combines multiple antifungal medications with surgical removal or drainage of the abscess; a 2024 French study of 23 patients cited by the CDC found surgery patients showed relatively favorable outcomes, but even optimal treatment does not always save patients.

The CDC is calling for systematic national reporting mechanisms to better track the pathogen, noting the United States currently has no formal nationwide surveillance system for it — which makes it hard to gauge the true scale of infections or identify transmission routes.

The fungus is rarely detected in natural environments, and patients' exposure histories vary widely, so no specific infection source has been identified.

Public health officials are urging clinicians to consider fungal pathogens, including *C. bantiana*, when evaluating patients with brain abscesses of unclear origin.

California's health department has already asked medical institutions and laboratories to cooperate in identifying and reporting related infections, and the CDC says expanded laboratory reporting and further epidemiological investigation are needed to determine what is driving the rise.