Soil fungi cause a significant number of serious lung infections in 48 of the 50 states and the District of Columbia, including many areas long thought to be free of deadly environmental fungi, according to a study by researchers at the Washington University School of Medicine in St. Louis.
Research from the 1950s and 60s suggested that fungal infections of the lungs were only a problem in certain parts of the country. The new study, available online in Clinical Infectious Diseases, shows that this is no longer the case. Doctors relying on an outdated map of disease-causing fungi may miss signs of a fungal lung infection, leading to delayed or incorrect diagnosis, the researchers said.
Every few weeks I get a call from a doctor in the Boston area – a different doctor each time – about an issue they can’t solve. They always start by saying, “We don’t have a story here, but this really looks like a story.” I say, “You call me all the time about this. You do have a story.”
Andrej Spec MD, lead researcher and associate professor of medicine, Washington University School of Medicine in St. Louis
Histoplasmaor histo, is one of the three main types of soil-borne fungi that cause lung infections in the United States. Histoplasma found in the midwest and parts of the east, Coccidioides in the South West, and Blastomyces in the Midwest and the South. But a growing number of case reports and anecdotes suggest that all three have expanded beyond their traditional range in recent decades, likely due to climate change.
People get fungal lung infections after inhaling spores from fungi in the soil. The spores become airborne when soil is disturbed by farming, landscaping, construction, or even just by people walking around in fungus-rich environments like caves. Most healthy adults and children can easily fight off a yeast infection, but infants, older adults, and people with compromised immune systems may develop fever, cough, fatigue, and other symptoms. Fungal lung infections can easily be mistaken for bacterial or viral lung infections such as COVID-19, bacterial pneumonia, and tuberculosis.
“People with fungal infections of the lungs often spend weeks trying to get a proper diagnosis and appropriate treatment, all the while feeling terrible,” said lead author Patrick B. Mazi, MD, a clinical fellow in infectious diseases. “They usually go to multiple health care visits with multiple options to test and diagnose, but the doctor just doesn’t look at a yeast infection until they’ve exhausted all other options.”
Spec, Mazi and colleagues set out to determine where soil fungi are making people sick today. The Centers for Disease Control and Prevention (CDC) last revised its maps of pathogenic fungi in 1969.
The researchers calculated the number of fungal lung infections nationwide from 2007 to 2016 using Medicare fee-for-service claims from all 50 states and the District of Columbia. Using the patients’ addresses to identify counties of residence, they calculated the number of cases per 100,000 person-years for each county. (Person-years are a way to adjust for the fact that counties can have very different population sizes; one person on Medicare for one year is one person-year). Counties with more than 100 cases of cholera Histoplasma or Coccidioidesor 50 cases caused Blastomycesper 100,000 person-years were defined as having a significant number of fungal infections in the lungs.
Of the 3,143 counties in the United States, 1,806 had a significant number of lung infections caused by Histoplasma339 of Coccidioides oath 547 of Blastomyces. These counties were spread across most of the United States. Of the 50 states plus DC, 94% had at least one county with a problem Histoplasma lung infections, 69% with Coccidioides and 78% with Blastomyces.
“Fungal infections are much more common than people realize and they spread,” said Spec. “The scientific community has underinvested in researching and developing treatments for fungal infections. I think that’s starting to change, but slowly. It’s important for the medical community to realize that these fungi are really everywhere these days and that we we need to take them seriously, including when considering diagnoses.”
Washington University School of Medicine in St. Louis
Dear PB, and more. (2022) Geographic distribution of dimorphic mycoses in the premodern United States. Clinical Infectious Diseases. doi.org/10.1093/cid/ciac882.