Researchers at the US Centers for Disease Control and Prevention (CDC) have warned of a significant increase in cases of the discovery of a rare fungus known as “Cladophialophora bantiana”, infection with which is associated with a mortality rate ranging between 60 and 70%, after cases recorded in an American reference laboratory nearly quadrupled between 2023 and 2025.
A report published by the center stated that researchers detected 48 confirmed cases and one probable case of infection with the fungus in clinical samples collected during the period from January 2009 until July 2026, indicating that the absence of a regular national system for monitoring the infection makes determining the extent of its actual spread difficult.
Mushroom targets the brain
Cladophialophora bantiana is a type of dark mold found in the environment, including soil and decaying organic matter. It is characterized by its tendency to infect the central nervous system, where it can cause the formation of dangerous brain abscesses.
These abscesses can lead to inflammation and swelling in the surrounding tissues, and the appearance of neurological symptoms that vary depending on the location and severity of the injury. Symptoms may include headaches, nervous disorders, and problems with vision and memory.
The report data showed that 43 out of 49 cases, or about 88%, were discovered in samples taken from tissue inside the skull, while the fungus was detected in six lung samples, or 12%.
The way the fungus reaches the human body is still not fully understood. Researchers believe that infection occurs as a result of inhalation, or entry through a skin infection, before being transmitted to the brain in some cases.
Noticeable increase in cases
According to a report published on the New York Post website, the number of cases discovered by a specialized reference laboratory at the University of Washington ranged between one and five cases annually during the period from 2009 to 2023, before rising to eight cases in 2024, then to 14 cases in 2025.
The increase was not limited to the total number of cases; The detection rate of the fungus compared to the central nervous system samples that were examined increased by 210%, from an average of 8.4 cases per thousand samples during the period from 2017 to 2023, to 26 cases per thousand samples in 2025.
Fungal infections were recorded in 21 American states, in addition to Washington, D.C. The states with the most cases were California with six cases, Florida with five cases, Texas with five cases, and Pennsylvania with four cases.
Ambiguous risk factors
One of the main concerns for researchers is that infection with this fungus is not limited to people with weak immune systems. The medical literature on which the report was based indicates that about half of the patients had no known previous conditions that weakened immunity.
This means that having a healthy immune system does not rule out infection, although the fungus is rare and the risk factors associated with it are still unclear.
The infection is more difficult to deal with because its manifestations can resemble other diseases, including brain tumors. Its diagnosis and treatment may be complex, and there is not yet sufficient evidence to determine a unified treatment regimen that guarantees the best results for all patients.
Is climate change a cause?
“The reasons for the apparent increase in the number of cases remain unknown,” the CDC says.
A French study was previously published in 2024 that dealt with 23 patients with fungal infections, and indicated the importance of surgical intervention in some cases. However, the fact that the rise in cases in different regions coincided with periods of high temperatures is not sufficient on its own to prove the existence of a causal relationship with climate change.
One study showed that cases of infection with this fungus saw a similar rise in France in 2022, the year in which the highest temperatures were recorded there since 1900.
Has the infection reached the Arab world?
Dark fungus infection that targets the brain is not limited to the United States or Europe. Medical studies have documented cases in Asian countries and the Middle East.
Among them is a study published in the journal Neurosciences in 2023, which dealt with 12 cases of brain infection with dark fungi, diagnosed at King Faisal Specialist Hospital and Research Center in Riyadh.
The study showed that one of the cases was caused by the Cladophialophora bantiana fungus itself, while other fungal species caused the remaining infections.
The patient infected with this fungus was a young man in whom no apparent immune weakness was detected, despite a comprehensive medical evaluation.
This case confirms that the fungus is not geographically limited to the United States, but it does not mean that there is an outbreak of it in Saudi Arabia or the Arab region.
In light of the results, the researchers called for developing more regular mechanisms for reporting cases of infection, and encouraging clinical laboratories to document the cases they discover, which helps identify risk factors, potential sources of exposure, and patterns of spread of the fungus more accurately.
The importance of this step lies in the fact that the 49 cases included in the report do not necessarily represent all the infections that occurred during the period studied, especially in light of the absence of a comprehensive national monitoring system and the possibility that some cases will not be detected or diagnosed correctly.
The center warns that there is no federal system to track and monitor the disease. Experts are still not sure how the fungus spreads, and do not yet know the reason for the continuous rise in the number of infections.