Analysis Reveals Nationwide Spread of Three Historically Regional and Potentially Life-Threatening Fungal Infections

Fungi Coccidioides immitis, saprophytic stage, 3D illustration showing fungal arthroconidia. Pathogenic fungi that reside in soil and can cause infection coccidioidomycosis, or Valley fever. (Kateryna Kon, Shutterstock)

February 17, 2023

Three fungal infections have spread outside their usual regions of infection and now appear in at least half of the United States. Maps that shape how clinicians diagnose and treat these infections haven’t been updated in more than 50 years. A new Clinical and Translational Science Awards (CTSA) Program–funded analysis of national health records has redrawn those maps to potentially speed detection and treatment outside areas where the three infections have historically been found.

The three fungal infections, or mycoses, are histoplasmosis, coccidioidomycosis (commonly called Valley fever), and blastomycosis. They are caused by fungi typically found in soil or on plants. The fungi can cause infection when people inhale them, and severe infections can be life-threatening.

Researchers from Washington University in St. Louis and the University of Minnesota analyzed patient data from more than 45 million Medicare recipients ages 65 or older in the Centers for Medicare & Medicaid Services Chronic Condition Warehouse. The study authors searched records from 2007 to 2016 for diagnoses of the three mycoses. They determined the incidence of each fungal infection in every U.S. county and identified counties with considerable levels.

The new analysis reveals that it may be time to consider these mycoses beyond their traditional boundaries. The researchers found that all three fungal infections had spread well beyond the boundaries in the national distribution maps last updated in 1969. Most states now have at least one county with considerable infection levels of one or more of the three mycoses.

A total of 94% of U.S. states had clinically significant rates of histoplasmosis in at least one county. Blastomycosis was found at clinically significant rates in at least one county in 78% of states, while 69% had clinically significant rates of coccidioidomycosis.

Using the modern data, the study authors created new U.S. maps detailing the expanded distributions of the three mycoses. A better understanding of the current ranges of the mycoses could help clinicians outside the historical regions recognize and treat these fungal infections sooner.

The new analysis makes the “where” clear; the “why” is less certain. Possible culprits include known contributors, such as travel-related exposure. The researchers also pointed to climate change, which has been shown to increase infection rates.

The research was funded by NCATS’ CTSA Program, the National Institute of Arthritis and Musculoskeletal and Skin Diseases, and Mayne Pharma.

Learn more about the study findings in Clinical Infectious Diseases.