Rising temperatures may cause fungi to be more dangerous to our health, a new study reveals.
While bacteria and viruses are well known drivers of infection and disease, pathogenic fungi have so far only caused minor problems for healthy people.
This is usually because the human body temperature is typically too hot for infectious fungi to survive.
But that might be about to change, researchers at Duke University in North Carolina warn.
This may ring alarm bells for fans of the hit dystopian HBO series, ‘The Last of Us’, in which a heat-adapted fungus takes over humans.
“That’s exactly the sort of thing I’m talking about - minus the zombie part!” says study co-author Asiya Gusa.
What are pathogenic fungi?
Pathogenic fungi are fungi that cause disease in humans and other organisms.
Among the approximately 300 fungi known to be pathogenic to humans, Candida, Aspergillus and Cryptococcus are some of the most well known.
They are currently most dangerous to immunocompromised people who lack the defences to prevent their spread.
How could rising temperatures make fungi more dangerous?
Rising global temperatures are predicted to increase fungal diseases in humans, but they could also make those diseases more serious.
Studying the impact of heat stress on fungi, researchers found that higher temperatures led to rapid genetic changes in the human fungal pathogen Cryptococcus.
Higher temperatures were found to stimulate the fungus’s transposable ‘jumping genes’, accelerating the number of mutations and leading to adaptations in the way the genes are used and regulated.
“These mobile elements are likely to contribute to adaptation in the environment and during an infection,” says Gusa. “This could happen even faster because heat stress speeds up the number of mutations occurring.”
This could lead to higher heat resistance, drug resistance and disease-causing potential, according to the research published in the science journal PNAS.
“This is a fascinating study, which shows how increasing global temperature may affect the fungal evolution in unpredictable directions… One more thing to worry about with global warming,” says Dr Arturo Casadevall, chair of molecular microbiology and immunology at Johns Hopkins University.
Is fungi on the World Health Organization's radar?
Fungal infections are already deadly, killing around 1.7 million people per year - and they're a "growing health threat", according to the World Health Organization (WHO). They are also becoming increasingly resistant to antifungal drugs used to treat them - and we currently lack alternatives.
In October 2022, the WHO released its first ever fungal priority pathogens list. "Despite posing a growing threat to human health, fungal infections receive very little attention and resources globally," the report reads.
It aims to increase global surveillance of fungi that are developing antimicrobial resistance, fund research and development into the issue, and advise on public health action.
Four fungi are placed in the 'critical priority group', including pathenogenic yeasts Cryptococcus neoformans, Candida auris and Candida albicans, along with Aspergillus fumigatus, a common mould found in soil.
Priority order placed public health first - including case numbers and deaths - followed by antifungal resistance, knowledge gaps and global spread.
A further seven are listed as high priority, many of which affect tropical regions most frequently - so could spread if the planet heats up.
"There is evidence to suggest that both the incidence and geographic range of fungal infections are expanding globally due to climate change," the report says.