Life-threatening fungal infections are on the rise in the United States. Their growth has been described as "alarming" by the U.S. Centers for Disease Control and Prevention (CDC,) with one emerging species in particular considered an "urgent threat" to human health.
Between 2020 and 2021, the U.S. saw a 95 percent rise in clinical cases of infections with the yeast Candida auris, roughly a third of which were fatal. Equally concerning was the tripling in the number of Candida cases that were resistant to common antifungal treatments.
"Candida auris has spread globally in a very short space of time," Nicholas Money, a world-leading mycologist and professor of biology at Miami University in Ohio, told Newsweek. "It's a hospital-acquired infection, so it tends to affect older patients. It's a really nasty thing, and it's growing."
The fungus was first detected in the ear of a woman in Japan in 2009. Since then, it has spread around the world, making its way into hospital patients through their catheters and multiplying in the blood. The fungus can also be spread via surfaces like bed rails, doorknobs, and blood-pressure cuffs. For those with severe infections, the mortality rate can be as high as 60 percent, although this is usually in patients who were extremely sick before the fungus took hold.
But what is driving the evolution of this hyperaggressive, incurable fungal infection. And what can we do about it?
"Some of the very prominent scientists in my field have linked this to climate change," Money said. "Now, of course, I'm not denying climate change, but if you look at global temperatures, they've increased by 1½ degrees Celsius over the last 140 years—that's child's play for fungi. They're totally unaffected by this.
"Instead, I believe there are other things going on in nature that have changed the development of these fungi that are responsible for making them so dangerous," Money added.
Since the 1980s, antifungal drugs have been used widely in both health care and—more significantly—agricultural contexts. "In agriculture, we use millions of tons of the same kinds of compounds that we use to treat fungal infections in us," Money said. "Apples, for example, and other fruits are sprayed with these antifungal agents that are frighteningly similar to the drugs that we use to control life-threatening human infections. So, I think agriculture really is what's to blame here."
By exposing the fungi in our crops to these antifungal agents, we are essentially selecting for the hardier, more resistant fungi, allowing them to survive while eliminating their competition. Over time, this drives the evolution of drug-resistant infections that become increasingly harder to treat.
This theory aligns with previous research into antifungal resistance in other species of Candida yeast, driven by the widespread use of antifungal medications. "There has been concern about antibiotic resistant bacteria for decades and fears about the widespread use of antibiotics in agriculture, but I think we really need to be looking at these fungicides too because they represent a downstream, very negative effect on human health," Money said.
These fungicidal agents also have the potential to harm our health directly, too. "The quantity that you're eating in, say, an apple is pretty small, but absolutely the potential is there [to cause damage,]" Money said. "These antifungal agents have already been shown to impact the body; for example, they have been shown to affect liver function when they build up in the body."
Money added that, even though climate change might not be driving the emergence of hyperaggressive fungal infections, that doesn't mean it isn't affecting our health. "Warmer and wetter weather has already been associated with increased numbers of airborne fungal spores, and these particles are one of the principal causes of asthma and allergic rhinitis," he said.
Money discusses these ideas further in his upcoming book, Molds, Mushrooms and Medicine: Our Lifelong Relationship With Fungi, published by Princeton University Press. He will be talking more about our relationship with fungi at the New Scientist Live event, taking place on Saturday, 12 October and Sunday, 13 October at ExCeL London, England. The event can also be streamed online.
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