Fungal diseases have devastated many animal and plant species. Humans and other mammals, however, have been mostly spared. There may be two reasons for that. Their body temperatures are too warm for most fungi to replicate in. Mammals also have powerful immune systems. But climate change may be bringing new fungal threats to human health.
From 2012 to 2015, versions of a deadly fungus showed up at the same time in Africa, Asia and South America. It’s named Candida auris (Kan-DEE-da OAR-is). All versions are from this same species. But the versions on each continent had a different genetic makeup. So the fungus wasn’t spread by infected travelers, concluded Arturo Casadevall. He is a microbiologist at the Johns Hopkins Bloomberg School of Public Health in Baltimore, Md.
C. auris is a health concern because it can cause deadly infections in people. To infect humans, the fungus had to become more tolerant of warmer temperatures. C. auris may have adapted to the average normal body temperature of humans. That is about 37° Celsius (98.6° Fahrenheit). And climate change may have made this possible, Casadevall and his colleagues now propose.
If true, the researchers write, C. auris “may be the first example of a new fungal disease emerging from climate change” that poses a risk to people. The researchers reported their finding online July 23 in mBio.
There have been nearly 700 U.S. cases of C. auris infections since mid-2016. Those cases have occurred in hospitals and other healthcare facilities in 12 states. Some of the patients have died. Cases also have turned up in more than 30 other countries.
The fungus causes dangerous infections of the blood, brain and heart. An invasive infection can be fatal 30 to 60 percent of the time, studies show. Some infections are resistant to antifungal medicines.
Past work has shown a fungus can grow at warmer temperatures in a lab. “There are millions of fungal species out there,” Casadevall says. “As they adapt to a warmer climate, some of them will then have the capacity to breach our thermal defenses.”
Other fungi are wreaking havoc on many animals and plants. These include frogs, snakes and trees. “A lot of our fellow creatures are being wiped out,” Casadevall says. In general, mammals are “remarkably resistant to invasive fungal diseases.” But bats are mammals, too. And they have been affected by outbreaks of a fungus that causes white-nose syndrome. Bats can get this fungus in part because their body temperature drops during hibernation.
“The fungal kingdom is just so vast,” Casadevall says. If another fungus dangerous to humans evolves, “who knows what it will do to us?”