Warming climates, drug overuse and poor detection methods are fuelling a rapid rise in deadly fungal infections

Every day, people unknowingly inhale hundreds of invisible fungal spores. Most pass through harmlessly. But some—like the Aspergillus fungus—are becoming increasingly dangerous. Once a quiet recycler of nature’s debris, it is now mutating into a global health threat that can eat humans from the inside out.

Three main strains—Aspergillus flavus, A. fumigatus, and A. niger—are leading this fungal onslaught. These moulds thrive in soil, on grains, and even animal feathers. Their spores can infect lungs, rot crops, and contaminate food all at once. In people with weakened immune systems, especially hospital patients, they cause life-threatening infections. But even the healthy may soon be at risk.

A recent study by The University of Manchester, led by Dr Norman van Rhijn, paints a grim picture of Aspergillus’s future. Using climate models, researchers mapped how these fungi might spread under high emissions scenarios. The results: a dramatic expansion across Europe, North America and Asia. For example, A. flavus could grow its European range by 16%, while A. fumigatus might expand by a staggering 77.5%, putting millions more at risk.

Why is this happening? The answer lies in a deadly mix of rising temperatures, misuse of fungicides, and genetic adaptability. Farmers commonly spray crops like wheat and peanuts with azole fungicides. Doctors use similar drugs to treat patients with fungal lung infections. This overlap is pushing Aspergillus to evolve resistance, much like bacteria becoming immune to antibiotics.

In the clinic, this means trouble. Patients infected with drug-resistant strains of Aspergillus face mortality rates over 50%. Doctors are left with few alternative treatments—many of which come with toxic side effects. Meanwhile, hospitals already struggle with outbreaks following construction work or during dust storms. The added burden of climate-driven surges could overwhelm healthcare systems.

On farms, the consequences are equally devastating. Mould outbreaks contaminate grains with deadly mycotoxins. A single year of uncontrolled Aspergillus growth can cost the U.S. corn industry over $1 billion. As heat and humidity increase, so do the odds of large-scale crop failures. Farmers may try to spray more fungicides in response—further fuelling the resistance spiral.

The dangers are not confined to humans. Aspergillus also infects honeybees and animals, while its spread reshapes ecosystems. In Africa, some regions may become too hot for the fungus to survive, but in others, especially temperate zones, it will thrive. The global reshuffling is complex—and unpredictable.

Experts now urge urgent action. The World Health Organization added Aspergillus to its list of emerging health threats in 2022. But progress is slow. Only 10% of the world’s fungi are officially described. Fewer still have sequenced genomes. This lack of basic knowledge hampers vaccine development and leaves doctors flying blind.

To stay ahead, researchers are calling for a three-pronged strategy: coordinated global monitoring of fungal spores, smarter use of fungicides, and investment in new antifungal drugs. Air sensors, crop testing, and hospital surveillance must work together to flag threats early. Improved building ventilation can reduce indoor spore exposure. And slashing greenhouse gas emissions may help curb the environmental shifts driving fungal expansion.

We’re facing an ancient organism armed with modern advantages—heat, resistance, and our own complacency. Without swift and sweeping action, a mould that once fed on leaves could soon prey on us, silently and fatally.