Every year, I set a small reading goal and track my progress in one of those reading apps. I started using Storygraph last year and set a goal of 12 books. Small for some, but I met last year’s goal with no problem. 🙂
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For my first book this year, I read Blight: Fungi and the Coming Pandemic by Emily Monosson. While blight is commonly defined as a plant disease caused by fungi, and the book does cover all things about fungal plant diseases, I found a fact from the book quite interesting: that fungal disease was a rare occurrence just decades ago.
The thermal barrier that prevents fungal infections
Most fungi preferred lower temperatures ranging from 18°C to 30°C. Humans, and other mammals, fall out of this range, creating a “thermal barrier” that keeps fungal infections at bay. However, as climate change occurs, this can slowly change.
In the book, Monosson mentioned the work of Arturo Casadevall, a microbiologist and immunologist at Johns Hopkins University, and Monica Garcia-Solache, a geneticist at Brown University. In 2010, they co-authored a piece in the microbiology journal mBio, Global Warming Will Bring New Fungal Diseases for Mammals, that talks about this idea. They hypothesized that climate change could allow fungi to live in new areas that used to be too warm, and at the same time, as fungi evolve to closer and closer to human body temperature thanks to climate change, they can breach this thermal barrier and cause new diseases in humans.
Examples of thermotolerant fungi
This is what seemed to happen with Candida auris. In 2009, it was first isolated from the ear canal. Since then, this fungus has caused outbreaks in hospitals around the world. The first case of C. auris was reported in the U.S. in 2016 and by 2023, there were over 4,000 infections just that year in the U.S. (You can find more stats on the CDC’s C. auris tracker). Despite their short documented history in humans, they’re already resistant to multiple antifungal drugs.
C. auris is just one example of fungus that have breached the thermal barrier, leading to more widespread infection in humans. Other examples include valley fever which was rare at the start of the 2000s but has increased seven times in just two decades. Another fungus, Cryptococcus deuterogattii, once restricted to tropical and subtropical climates, made its way to the Pacific northwest and western Canada where it caused hundreds of infections. Compared to other closely related fungi, this particular fungi could better tolerate increased temperatures so this trait could have helped it spread across the world.
Even changes in temperature over just small distances can show how fungi can evolve to be more heat tolerant. Last year, Casadevall published a paper showing that fungi from warmer neighborhoods in Baltimore, MD were more tolerant to heat than fungi of the same species from cooler neighborhoods.
The future are fungi
It’s not just climate change behind the growing threat of the rise in fungal infections in the future. Even in the last decade, scientists have estimated that the number of fungal infections annually has doubled. What’s clear though is that when fungi take hold in a new environment, they’re there to stay. Climate change, antifungal resistance, the lack of vaccines against fungi, and limited surveillance are some of the problems that scientists and clinicians need to tackle to keep fungal infections from running rampant in the future.
Featured image by Ajay Kumar Chaurasiya (CC-BY-SA 4.0).
