Fungi That Cause Lung Infections May Be Spreading Across the U.S. - Smithsonian Magazine

Histoplasma under a microscope Smith Collection / Gado via Getty Images

Harmful, soil-dwelling fungi may be more widespread throughout the United States than scientists and medical professionals previously thought.

Past research, conducted in the 1950s and '60s, suggested disease-causing fungi only lived in certain areas of the country. But scientists now believe the fungi are spreading and causing serious lung infections throughout the nation.

As a result, doctors are relying on outdated maps of the fungi's ranges, and they may be misreading the symptoms of potentially severe fungal lung infections, suggests new research published this month in the journal Clinical Infectious Diseases.

The researchers looked at three main kinds of soil fungi that can cause lung infections in the U.S.: histoplasma, coccidioides and blastomyces. During construction, farming, landscaping and other disruptive activities, the soil can release fungal spores into the air. Once airborne, the spores make their way into the lungs and breathing passages of nearby humans.

Healthy adults and children can typically fend off a potential fungal infection, but some people—such as older adults, infants and individuals with compromised immune symptoms—have more trouble. Breathing in these fungi can cause them fatigue, fever, cough and other symptoms. Doctors, meanwhile, easily mistake these fungal infections for something else, such as Covid-19, tuberculosis or bacterial pneumonia.

"There's probably a significant number of patients who were never diagnosed directly and really suffered a lot more morbidity from their disease," George Thompson, an infectious disease specialist at the University of California, Davis, who was not involved with the study, told NBC News' Angela Yang and Aria Bendix.

The map of disease-causing fungi used by the Centers for Disease Control and Prevention dates to 1969, per the study. As such, doctors in parts of the country with no history of these pathogens may focus their attention on other possible causes of illness.

Historically, researchers thought histoplasma, also called histo, existed primarily in the Midwest and along parts of the East Coast, while coccidioides inhabited the Southwest and blastomyces lived in the Midwest and the South.

But, based on anecdotal evidence and case reports, the study's authors had a hunch that all three fungi may have expanded outside of their typical regions, assisted by human-caused climate change, which is shifting the areas hospitable to various pathogens.

The top row shows the historic range of histoplasma (red), blastomyces (blue) and coccidioides (green) on maps created based on data from the 1950s. The bottom row shows the fungi's range using data from 2007 to 2016. Patrick Mazi and Andrej Spec / Washington University

"Every few weeks, I get a call from a doctor in the Boston area—a different doctor every time—about a case they can't solve," says study co-author Andrej Spec, an infectious disease specialist at the Washington University School of Medicine, in a statement. "They always start by saying, 'We don't have histo here, but it really kind of looks like histo.' I say, 'You guys call me all the time about this. You do have histo.'"

To get a better handle on the three fungi, the researchers analyzed Medicare claims for fungal lung infections from all 50 states and the District of Columbia between 2007 and 2016. They used the patients' home addresses to estimate the prevalence of cases in each county.

They discovered a significant number of fungal lung infections in 48 states and D.C., including in places with no historic record of the three fungi.

Out of 3,143 total U.S. counties, the researchers found meaningful numbers of infections caused by histo in 1,806 counties, by coccidioides in 339 counties and by blastomyces in 547 counties during the nine-year study period.

The new research does have a few limitations, though, reports LiveScience's Nicoletta Lanese. The scientists only looked at data for Medicare beneficiaries who were 65 and older, so it's possible they missed some additional cases. And their methods did not account for patients who may have picked up a fungal infection somewhere other than their home county.

Still, the evidence suggests these infections may be more common than patients, doctors and public health officials realize.

"It's important for the medical community to realize these fungi are essentially everywhere these days and that we need to take them seriously and include them in considering diagnoses," Spec says in the statement.

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