Infectious disease experts say the average human body temperature of 98.6 degrees Fahrenheit has long been too hot for most fungi to thrive. But as global temperatures rise, some fungi may adapt to tolerate greater heat stress, including conditions inside the human body, research suggests. Research shows that climate change may create conditions for some disease-causing fungi to expand their geographic range.
“As fungi are more consistently exposed to elevated temperatures, there is a real possibility that some fungi that were previously harmless suddenly became potential pathogens,” said Peter Pappas, an infectious disease specialist at the University of Alabama at Birmingham.
Deaths from fungal infections are on the rise, public-health experts said, due to a growing population of people with weakened immune systems, who are more vulnerable to serious fungal disease. The Centers for Disease Control and Prevention projects that at least 7,000 people will die from fungal infections in the US in 2021, up from hundreds of thousands each year around the 1970s. There are few effective and non-toxic drugs to treat such infections, he said.
In the video game and HBO show “The Last of Us,” a fungus infects people en masse and turns them into monstrous creatures. The fungus is based on an actual genus, Ophiocordyceps, which includes species that infect, paralyze, and kill insects.
Infectious disease experts said there are no known sources of Ophiocardyceps infection in people, but they said rising temperatures have facilitated the spread of the killer fungus in the show, allowing other fungi to better adapt to human hosts and move into new geographic ranges. may be motivated to expand. ,
A January 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.
Duke University researchers grew 800 generations of a type of Cryptococcus, a group of fungi that can cause severe illness in people in conditions as low as 86 degrees Fahrenheit or 98.6 degrees Fahrenheit. The researchers used DNA sequencing to track changes in the genome of fungi with a focus on “jumping genes” – DNA sequences that can move from one place on the genome to another.
Such gene movement can lead to mutations and changes in gene expression, said Asiya Gusa, a study co-author and postdoctoral researcher in Duke’s Department of Molecular Genetics and Microbiology. In fungi, Dr. The movement of the genes may play a role in allowing the fungus to adapt to stresses, including heat, said Gusa.
Dr Gusa and his colleagues found that the rate of movement of “jumping genes” in Cryptococcus was five times higher in warmer temperatures.
Cryptococcus infection can be fatal, especially in immunocompromised people. The Centers for Disease Control and Prevention states that brain infections caused by the Cryptococcus fungus kill at least 110,000 people each year.
Infectious disease experts said that Candida auris, a highly lethal fungus that has been reported in nearly half of US states, also appears to have adapted to warmer temperatures.
“Fungi does not spread from person to person, but through fungal spores in the air,” Dr Gusa said. “They’re in our homes, they’re everywhere.”
An analysis published last year in the journal Clinical Infectious Diseases says some potentially deadly fungi found in soil, including Coccidioides and Histoplasma, have significantly expanded their geographic range in the US since the 1950s. Lady Speck, a co-author of the analysis and an associate professor of medicine at Washington University School of Medicine in St. Louis, said warming temperatures, as well as other environmental changes linked to climate change, may play a role in this spread. ,
Cases of Coccidioidomycosis or Valley Fever, a disease caused by Coccidioides, were once mostly confined to the Southwest, Dr. Speck said. Significant numbers of people are now being diagnosed in most states. Histoplasma infection, once common only in the Midwest, has been reported in 94% of states, the analysis said. Dr Speck said Histoplasma is also spread through bat droppings and climate change has been linked to changing bat migration patterns.
The World Health Organization has identified Cryptococcus, Coccidioides, Histoplasma and Candida auris among the fungal pathogens of greatest danger to humans.
“We say these fungi are rare, but this must be the most common rare disease because they are everywhere now,” Dr Speck said.