Nationwide Problem: Serious Lung Infections Caused by Soil Fungi

Histoplasma Fungal Spread

The fungus Histoplasma, which causes lung infections, was concentrated in the Midwest in the 1950s and 60s (top map), but now causes significant disease throughout much of the country (bottom). Researchers at Washington University School of Medicine in St. Louis discovered that the three main kinds of soil fungi that cause lung infections have all expanded their ranges in recent decades. Reliance on outdated maps could be causing delayed or missed diagnoses. Credit: Patrick Mazi and Andrej Spec/Washington University

Outdated maps of disease-causing fungi may lead to delayed and missed diagnoses.

Fungi in the soil cause a significant number of serious lung infections in 48 out of 50 states and the District of Columbia, including many areas long thought to be free of deadly environmental fungi. This is according to a recent study by researchers at Washington University School of Medicine in St. Louis.

Studies from the 1950s and 60s indicated that fungal lung infections were a problem only in certain parts of the country. That is no longer the case, shows a new study, which was published on November 11 in the journal Clinical Infectious Diseases. Doctors who rely on outdated maps of disease-causing fungi may miss the signs of a fungal lung infection, resulting in delayed or incorrect diagnoses, the researchers said.

“Fungal infections are much more common than people realize, and they’re spreading.” — Andrej Spec, MD

“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,” said senior author Andrej Spec, MD, an associate professor of medicine and a specialist in fungal infections. “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.’”

Histoplasma, or histo, is one of the three main species of soil fungi that cause lung infections in the U.S. Historically, Histoplasma was found in the Midwest and parts of the East, Coccidioides in the Southwest, and Blastomyces in the Midwest and the South. But a growing number of case reports and anecdotes suggest that all three have expanded out of their traditional ranges in recent decades, most likely due to climate change.

The three main species of fungi that cause lung infections in the U.S. — Histoplasma (red), Blastomyces (blue) and Coccidioides (green) — have all expanded their ranges in recent decades. These maps were created based on data from 1955 (top row) and 2007-2016 (bottom row). Reliance on outdated maps may lead to delayed or missed diagnoses. Credit: Patrick Mazi and Andrej Spec/Washington University

People develop fungal lung infections after breathing in spores from fungi in the soil. The spores become airborne when the ground is disturbed by farming, landscaping, construction, or even just by people walking around in fungi-rich environments such as caves. Most healthy adults and children can fight off a fungal infection handily, but infants, older adults, and people with compromised immune systems may develop fever, cough, fatigue, and other symptoms. Fungal lung infections easily can be mistaken for bacterial or viral lung infections such as COVID-19, bacterial pneumonia and tuberculosis.

Histoplasmosis is an infection caused by a fungus called Histoplasma. The fungus lives in the environment, especially in soil that contains large amounts of bird or bat droppings. People can get histoplasmosis after breathing in the microscopic fungal spores from the air. Although most people who breathe in the spores don’t get sick, those who do may have a fever, cough, and fatigue. Many people who get histoplasmosis will get better on their own without medication, but in some people, such as those who have compromised immune systems, the infection can become severe.

“People with fungal lung infection often spend weeks trying to get the right diagnosis and appropriate treatment, and the whole time they’re feeling terrible,” said lead author Patrick B. Mazi, MD, a clinical fellow in infectious diseases. “They usually have multiple healthcare visits with multiple opportunities for testing and diagnosis, but the doctor just doesn’t consider a fungal infection until they’ve exhausted all other possibilities.”

Spec, Mazi, and colleagues set out to determine where soil fungi are sickening people today. The Centers for Disease Control and Prevention (CDC) last revised its maps of disease-causing 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’ home 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 correct for the fact that counties can have wildly different population sizes; one person on Medicare for one year is one person-year). Counties with more than 100 cases caused by Histoplasma or Coccidioides, or 50 cases caused by Blastomyces, per 100,000 person-years were defined as having a meaningful number of fungal lung infections.

Of the 3,143 counties in the U.S., 1,806 had meaningful numbers of lung infections caused by Histoplasma, 339 of Coccidioides and 547 of Blastomyces. These counties were distributed across the majority of the U.S. Across the 50 states plus DC, 94% had at least one county with a problem with Histoplasma lung infections, 69% with Coccidioides and 78% with Blastomyces.

“Fungal infections are much more common than people realize, and they’re spreading,” Spec said. “The scientific community has underinvested in studying and developing treatments for fungal infections. I think that’s beginning to change, but slowly. 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.”

Reference: “The Geographic Distribution of Dimorphic Mycoses in the United States for the Modern Era” by Patrick B Mazi, MD, John M Sahrmann, MA, Margaret A Olsen, PhD, Ariella Coler-Reilly, BA, Adriana M Rauseo, MD, Matthew Pullen, MD, Julio C Zuniga-Moya, MD, William G Powderly, MD and Andrej Spec, MD, 11 November 2022, Clinical Infectious Diseases.
DOI: 10.1093/cid/ciac882


View Comments

  • I've been telling my husband for a few years that this is a much bigger problem than people realize and will become far worse and that we'll be seeing it mentioned more bc it won't be able to be ignored for too much longer. It's not only climate change, any upset of the natural biome sets up the circumstances for pathogenic fungi to take advantage. We will be seeing fungal pathogens affecting plants and animals as well, I'm already seeing it in my local area since 2019. We have disrupted the natural environment on a massive scale.

  • "... most likely due to climate change."
    Without citing any study specifically intended to establish cause, they opine that the apparent increased range is "most likely" a result of climate change. There seems to be an uncritical mind set that because the climate has warmed, any changes in the environment MUST be a result of "climate change." Correlation does NOT prove causation! This could be a spurious correlation resulting from better data collection and improved diagnoses.

    • My husband is from eastern Virginia and he had blastomycosis back in the early 80s he was 16. Coon dogs died one boy lost a lung and all were very very sick.

  • Or can it be that it should be made illegal to use fertilizers in an air born (u know like spreading pig feces in the irrigation system) and polluting the water systems.

    • Well, as these are considered soil fungi, it's much more likely that they're spread by plowing and disking (disturbing the soil) during a breezy or windy day. I'd be for banning plowing and disking long before I'd get behind banning the spreading of organic fertilizers.

    • And you probably should stop blaming anything, including plants and fungi, for your personal fear of going to the doctor.

  • Climate change would make the ranges change northward. Instead, they are spreading randomly as would be caused by lots of dust being moved from one location to another--planes, trains, and automobiles. Or, it could be better detection.

    • Also, the US population has more than doubled since 1955, meaning that there are more people living in areas that were formerly 'free' of fungal diseases. With low population densities, there may not be enough people to trigger a concern if a small percentage catch a lung disease. In the frontier days, tuberculosis was called "consumption," and doctors probably couldn't tell TB, emphysema, chronic pneumonia, or silicosis from a fungal lung infection. I, and about 75% of my barracks at Fort Bliss (TX), had severe upper respiratory infections in 1968, which didn't respond to penicillin. Neither the army doctors or my civilian family doctor thought to treat us for fungal infections, despite "Valley Fever" being known in California since before the Gold Rush days. The maps clearly reveal that the spatial resolution of infections was poor in the 1950s.

      The unexamined assumption that the rate per capita of fungal infections was low in the 1950s may be wrong.

  • I had histoplasmosis in 2009. It took doctors 3 months to diagnose it. They thought I had lung cancer and I came close to a loboscopy. Two radiologists sent me into a CT machine to position a needle biopsy. They were able to get a sample from a nodule in the bottom of my lungs. I took itraconizole for several.months to get rid of it. Doctors speculated that the fungus came from Canada goose sh** from an adjacent farm being plowed or bat/bird s*** from one of my 9 fireplaces in my 200 year old house. Interestingly, histoplasmosis was featured on an episode of House, MD. Go figure.

  • I like how the maps show how like human activity is probably transferring it from place to place but they just can't help themselves and once again blame it on climate change. Looks like a emerald ash borer map where once it gets into an area it spreads out.

Washington University School of Medicine

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