Fungal infections are becoming increasingly dangerous, and a growing body of research suggests that rising temperatures could be a key factor. The human body’s average temperature of 98.6°F has traditionally been too hot for most fungi to survive, but as global temperatures have risen, some fungi are adapting to withstand more heat stress. This includes conditions within the human body, leading to a higher risk of fungal infections.
Climate change is also contributing to the spread of fungal diseases by creating ideal conditions for certain fungi to expand their geographical range. This is a serious concern, as some fungi that were once harmless could suddenly become potential pathogens as they are exposed to more consistent elevated temperatures.
Infectious-disease specialist Peter Pappas from the University of Alabama at Birmingham says, “As fungi are exposed to more consistent elevated temperatures, there’s a real possibility that certain fungi that were previously harmless suddenly become potential pathogens.” The number of deaths from fungal infections is increasing, partly due to the growing populations of people with weakened immune systems who are more vulnerable to severe fungal disease. In 2021, at least 7,000 people died in the U.S. from fungal infections, according to the Centers for Disease Control and Prevention. This is a significant increase from the hundreds of deaths each year reported around 1970.
Unfortunately, there are few effective and nontoxic medications to treat such infections, making it imperative that more research is done to better understand the impact of rising temperatures on fungal infections. The video game and HBO show “The Last of Us” is a fictional depiction of a mass fungal infection that turns people into monstrous creatures. The fungus in the show is based on a real genus, Ophiocordyceps, that includes species that infect insects and cause death. While there have been no known Ophiocordyceps infections in humans, the rising temperatures that facilitated the spread of the killer fungi in the show may be pushing other fungi to better adapt to human hosts and expand into new geographical ranges.
A recent study in the journal Proceedings of the National Academy of Sciences showed that higher temperatures may prompt some disease-causing fungi to evolve faster to survive. Researchers at Duke University grew 800 generations of a type of Cryptococcus, a group of fungi that can cause severe disease in people, under conditions of either 86°F or 98.6°F. The researchers used DNA sequencing to track changes in the fungi’s genome, with a focus on “jumping genes”—DNA sequences that can move from one location on the genome to another.
Study co-author Asiya Gusa, a postdoctoral researcher in Duke’s Molecular Genetics and Microbiology Department, explains that the movement of these genes can result in mutations and alter gene expression. In fungi, Gusa says, the movement of the genes could play a role in allowing fungi to adapt to stressors, including heat. The researchers found that the rate of movement of “jumping genes” was five times higher in the Cryptococcus raised in the warmer temperature.
Cryptococcus infections can be deadly, particularly in immunocompromised people. At least 110,000 people die globally each year from brain infections caused by Cryptococcus fungi, according to the Centers for Disease Control and Prevention. Another highly deadly fungus, Candida auris, has also been reported to have adapted to warmer temperatures. This fungus is not transmitted from person to person, but through fungal fragments in the air, and can be found everywhere from homes to healthcare facilities.