How climate change could have driven deadly fungus to infect humans

Rising global temperatures may have helped multidrug-resistant fungus Candidozyma auris evolve heat tolerance and enable it to infect humans and spread in hospitals worldwide. Scientists warn that climate change could drive similar fungal threats to emerge in the future

Fungi have moved from the margins of scientific concern into the mainstream of popular culture, largely through their portrayal in widely consumed works of fiction. The television adaptation and original video game The Last of Us vividly imagined a world devastated by a mutated cordyceps fungus that hijacks human hosts, while M. R. Carey’s novel The Girl with All the Gifts and its film adaptation presented a similarly unsettling vision of fungal infection reshaping society. These depictions, though speculative, have heightened public awareness of the real risks that fungi can pose, particularly in the context of rising antifungal resistance and the emergence of species such as Candidozyma auris.

Scientists have proposed that C. auris – the multidrug-resistant fungus formerly known as Candida auris – has emerged in part because of global climate change. The hypothesis suggests that the organism has evolved an unusual tolerance to heat, enabling it to breach the natural thermal barrier that normally protects mammals from fungal disease.

In 2019, Dr Arturo Casadevall and colleagues argued that rising global temperatures exerted selective pressure on fungi, forcing some species to adapt to higher ambient heat. They observed that C. auris grows at higher temperatures than its close relatives, making it capable of surviving at mammalian core body temperature, which excludes the majority of fungi.

Subsequent studies have reinforced this idea, noting the near-simultaneous emergence of genetically distinct C. auris clades on three continents – a pattern more consistent with a broad, climate-driven trigger than a single point of origin. Laboratory investigations have shown that C. auris can grow at up to 42 °C, significantly above the thermal limits of related species.

The fungus also tolerates high salt concentrations, suggesting environmental reservoirs in coastal and estuarine habitats. Isolates have been recovered from wetlands and marine environments, supporting the view that C. auris evolved in warm, saline ecosystems before crossing into healthcare settings.

Resistance to azole antifungal agents, widely used in agriculture and medicine, may also have contributed to its rise. Environmental exposure to antifungal compounds is thought to have favoured strains with multidrug resistance, creating a pathogen both able to thrive at human body temperature and difficult to treat.

Together, thermotolerance, halotolerance and antifungal resistance appear to explain how C. auris has adapted to human infection and established itself so rapidly in hospitals worldwide. Researchers caution that its success highlights a broader risk: as the climate continues to warm, more fungi may evolve the capacity to infect humans.