A rare fungus that attacks the brain is spreading in the US. The infection can kill up to 70% of patients.

A rare fungus that can cause serious infections in the brain is increasingly reported in the United States. Cladophialophora bantiana can cause brain abscesses, and the mortality rate in cases associated with it reaches 60-70%, according to a new report from the Centers for Disease Control and Prevention (CDC). The number of detected cases has increased significantly in recent years. Data from a reference laboratory at the University of Washington shows that between 2009 and 2023, between one and five cases were identified per year. However, the number rose to eight in 2024 and 14 in 2025. The CDC indicates that the detection rate increased by approximately four times between 2023 and 2025, according to Fox News. Affected States In total, between January 2009 and July 2026, researchers identified 48 confirmed and one probable case. The samples came from 21 American states and the District of Columbia. Most cases were reported in California, Florida, Texas, and Pennsylvania. An unusual aspect of the infection is that it does not exclusively affect people with a weakened immune system. Approximately half of the infected patients did not have a previously known condition causing immunodeficiency, according to the CDC. How the Fungus Reaches the Brain Cladophialophora bantiana is a pigmented, microscopic fungus with an affinity for the central nervous system. Specialists do not yet know exactly its reservoir in the surrounding environment or the mechanism by which people become infected. One of the hypotheses is that the spores are inhaled or enter the organism through a skin wound. Subsequently, the pathogen may reach the brain through the blood. Most known infections manifest as the formation of brain abscesses. Read also Mexico: "Brain-eating" Amoeba detected in Yucatan. Six lakes closed, authorities on alert The data analyzed by researchers supports this characteristic: out of the 49 cases identified, 43, or 88%, were detected in tissue samples from the central nervous system, and six cases were identified in the lungs. Mortality up to 70% Infections caused by C. bantiana are rare but extremely dangerous. The mortality rate is estimated at 60-70%, even when patients receive aggressive treatment. The diagnosis can also be difficult. The fungus can cause brain lesions that require complex investigations to be differentiated from other neurological conditions. Health authorities in California have recently asked doctors and laboratories to help identify cases of C. bantiana that have appeared since 2020, so that specialists can better understand the spread and risk factors. Specialists Do Not Know Why Cases Are Increasing The increase does not appear to be explained solely by the fact that more samples are analyzed. The CDC indicates that, in the period 2017-2023, an average of 8.4 cases per 1,000 samples from the central nervous system sent to the laboratory for fungal tests were detected. In 2025, the rate reached 26 cases per 1,000 samples, an increase of 210%. Currently, the United States does not have a national routine surveillance system for infections with Cladophialophora bantiana, and specialists say that more data are needed to determine if the phenomenon represents a real increase in incidence and what its causes are. The natural reservoir of the fungus and the factors that determine the occurrence of infections remain insufficiently known, according to the CDC. Editor: Sebastian Eduard