In general, humans are incredibly resistant to fungal infections because these organisms don’t thrive in warmth, said lead author Dr. Arturo Casadevall, chair of molecular microbiology and immunology at the Johns Hopkins Bloomberg School of Public Health in Baltimore.
But climate change could be increasing the tolerance of fungi to warmer temperatures, making them more likely to infect humans, Casadevall and his colleagues claim.
The researchers point to an emerging fungal pathogen, Candida auris, as the canary in the coal mine.
“We think this is a harbinger of things that may come,” Casadevall said of the fungus.
C. auris first appeared as an infection in humans in 2009, with genetically different strains sickening people on three different continents simultaneously, researchers said.
“What could be common to Venezuela, South Africa and India at the same time? These are different regions, populations, climates, you name it,” Casadevall said.
More than 30% of people with invasive C. auris infections die, according to the U.S. Centers for Disease Control and Prevention. There have been 685 confirmed cases and 30 probable cases in the United States since 2016.
Researchers argue that as the climate has gotten warmer, C. auris has adapted to the point that it can now thrive inside humans.
“We are warm-blooded and our temperatures are very effective at keeping most of the fungi out,” Casadevall said. “Most fungi can’t reproduce at our body temperature — about 95% of them cannot. Just being warm gives you a huge protection.”
That’s why human fungal infections have thus far been limited to such irritants as athlete’s foot, while plant life and cold-blooded creatures are susceptible to fungi that can harm and kill, Casadevall said.
However, fungi can quickly become accustomed to warmer temperatures, research has shown.
“Fungi can adapt to temperature pretty easily,” Casadevall said. “If you take a fungus into the laboratory and you slowly raise the temperature, they are able to live and reproduce at higher temperatures.”