Some fungi that can cause serious lung infections have spread to many parts of the United States. A Science News story on the expanded range of Histoplasma, Coccidioides and Blastomyces fungi hit a nerve with a lot of readers
They asked about the symptoms, treatments and testing for these fungal diseases. Some, like Judy Knudsen, whose husband Jack died from a Histoplasma infection in 2020, also wrote to share their own experiences with fungal infections. Others wanted to learn more about the fungi themselves.
I went back to Andrej Spec, a mycologist and infectious diseases doctor at Washington University School of Medicine in St. Louis whose team published the new range maps, for answers.
Spec and his colleagues are studying what has caused the fungi to spread and factors that may contribute to people getting sick. Those include changes to climate, weather patterns, extreme weather events like wildfires and floods, and even migration patterns of animals.
How do you catch these fungal infections?
People generally get infected by inhaling fungal spores released during the fungi’s normal life cycle. Human activities that disturb the soil where these fungi typically live — such as farming, gardening, construction, road work or archaeology — can also stir up dust and spores.
Besides soil, bird droppings and bat guano can be sources for Histoplasma. The fungi can infect bats and grow in the animals’ intestines. Birds don’t usually carry the fungus because birds’ body temperatures are typically around 39° Celsius to 42° C (102° Fahrenheit to 107° F). “They’re too hot for Histo, but their droppings are perfectly suited to grow” the fungus, Spec says.
The highest risk to people comes when bird and bat droppings have dried out. “People will try and sweep [the droppings], and then you kick up all that dust and inhale it.” Instead of sweeping, Spec advises, “hose it down and shovel it off.”
Wearing a mask can also help limit exposure. “Especially if you’re immunosuppressed, wear a mask.”It is possible for the fungi to get into a cut or scrape and start an infection in the skin, but those cases are very rare, Spec says. And people generally can’t pass the infection on to others, except in very rare cases in which an infected person has donated an organ or other body tissue, he says.
What happens in the body?
These three types of fungi are known as dimorphic fungi because they have two forms. In the soil, where they normally grow, they are molds. But at 37° C — human body temperature — they shape-shift into yeast, which can grow rapidly and spread more easily in the body.
When a person inhales the fungal spores, the fungi can infect the lungs where conditions are right for it to transform. People with healthy immune systems may have no symptoms or may develop mild flulike symptoms, including fever, cough, fatigue, chills and body aches. People with coccidiomycosis — the disease caused by Coccidioides — may also get a rash on their legs or upper body.
Source: sciencenews.org
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