It’s no game: Heat drives fungal mutations that affect health

Followers of “The Last of Us,” a 2013 video game release that’s now a top HBO drama series in the United States, know that the apocalyptic storyline begins with a heat-adapted fungus that takes control of humans and turns them into zombies. While there’s no zombie apocalypse on the horizon in real life, scientists say it’s true that fungi may pose more of a health problem in a warming world.

Researchers from Duke University School of Medicine have just published new findings to suggest that heat stress is a driver of genetic mutations in a fungus known to affect human health, called Cryptococcus deneoformans. Their tests in mice showed that the mutating fungus quickly adapted when the mice were infected, with mutations “dramatically elevated” at higher temperatures.

Cryptococcus and other fungi aren’t typically life-threatening to healthy people, although they can be fatal for people living with HIV/AIDS or another condition that leaves the immune system compromised.

But that may change in the future, the Duke scientists said, especially as heat stress increases the number of mutations affecting fungi and the speed at which they’re acquired.

“These are not infectious diseases in the communicable sense; we don’t transmit fungi to each other,” explains Dr. Asiya Gusa, a researcher who will join Duke University as an assistant professor later this year. “But the spores are in the air. We breathe in spores of fungi all the time and our immune systems are equipped to fight them.”

Cases of fungal disease are on the rise because more people are living with underlying health conditions and weakened immune systems, Gusa says. But the Duke study that looked at just three heat-stressed elements that drove genetic change in fungi found that 25 or more similar elements also could be affected by warming temperatures. At least one of the three changes could lead to drug resistance.

And the changes began to emerge within just ten days of infection in the mice, the scientists report.

It’s not the zombie apocalypse, to be sure, but the popularity of “The Last of Us” and its storyline makes it easier to draw some comparisons.

“That’s exactly the sort of thing I’m talking about — minus the zombie part!” said Gusa.

“It’s time to get serious about pathogenic fungi,” she added. “These kinds of stress-stimulated changes may contribute to the evolution of pathogenic traits in fungi both in the environment and during infection. They may be evolving faster than we expected.”