CDC Report Details Fourfold Rise in Rare Brain Fungus Detections

What was announced

Researchers from the University of Washington and the Centers for Disease Control and Prevention published an analysis of clinical samples tested for Cladophialophora bantiana. The organism is a neurotropic fungus, meaning it invades the central nervous system. Using broad-range fungal polymerase chain reaction (PCR), a molecular lab test that identifies fungal DNA in tissue, the laboratory identified 48 confirmed cases and one probable case between January 2009 and July 2026.

Annual detections ranged from one to five cases per year between 2009 and 2023. Cases rose to eight in 2024 and 14 in 2025. When adjusted for overall sample volume submitted to the lab, detections increased from 8.4 per 1,000 central nervous system tissue samples during 2017 to 2023 up to 26 per 1,000 in 2025. Most identified infections (88%) occurred in central nervous system tissue, while 12% were found in lung tissue. Patients had a median age of 68 years. Cases originated across 21 U.S. states and the District of Columbia, with the largest numbers coming from California, Florida, Texas, and Pennsylvania.

What it means

C. bantiana causes severe infections, mostly presenting as brain abscesses (pockets of pus in the brain). The disease carries a 60% to 70% mortality rate. Unlike many fungal pathogens, it often infects immunocompetent people, who have healthy immune systems, as well as immunocompromised patients.

The rise in lab detections suggests that infections may be increasing rather than just reflecting higher testing volume. Medical providers should consider testing for C. bantiana when treating patients with symptoms of a brain abscess. The report notes that combination antifungal therapy, alongside surgical removal or drainage of brain abscesses, may improve patient survival.

What the announcement does not tell us

The report explicitly states that the reasons for the recent rise in cases are unknown. It does not explain whether the fungus is becoming more dangerous or spreading more widely in the environment.

Because the study relies on data from a single reference laboratory, it lacks full patient histories. The authors had limited demographic, occupational, and medical data. The announcement does not identify specific environmental sources, exposure risks, or exact modes of transmission. Patient survival outcomes were also unavailable for almost all cases, except for one fatal case treated at the University of Washington Medical Center. Finally, national surveillance for C. bantiana does not exist in the United States, so overall nationwide case counts remain unknown.