Climate change fuels global spread of deadly Aspergillus fungus

New research warns that climate change will significantly expand the reach of Aspergillus fungi, intensifying the threat of fatal infections worldwide.

Illustration by Jonathan Knowles

By Anna Fadiah and Hayu Andini

Rising global temperatures are creating the ideal conditions for the Aspergillus fungus to expand its reach, potentially putting millions more people at risk of severe and often fatal infections. According to new research, climate change is driving the global spread of Aspergillus species—especially Aspergillus fumigatus and Aspergillus flavus—by making previously inhospitable regions suitable for their growth and survival.

The findings, released on Saturday and funded by Wellcome, underscore how the world is approaching a dangerous tipping point in the proliferation of fungal pathogens. These threats, often underestimated, are increasingly shaped by environmental changes such as heatwaves, droughts, and shifting rainfall patterns—all hallmarks of the climate crisis.

Fungi among the deadliest but most neglected health threats

Aspergillus fungi, which produce airborne spores invisible to the naked eye, are already responsible for severe respiratory illnesses, particularly among immunocompromised individuals. The World Health Organization (WHO) has designated A. fumigatus as one of the top four fungal threats to public health. This pathogen, often found in soil and decaying vegetation, can cause aspergillosis—a potentially deadly lung disease that may spread to other organs, including the brain.

The global mortality burden from invasive fungal infections is staggering. An estimated 3.8 million people die annually with such infections, and in about 2.5 million of those cases, the fungal pathogen is the primary cause of death. Despite this, mycology remains an underfunded and under-researched field. Over 90 percent of fungal species remain scientifically undescribed, according to a 2023 report by the UK’s Royal Botanic Gardens, Kew.

How climate change is shifting the fungal threat zone

The new study warns that if fossil fuel usage continues at current rates, the geographic range of Aspergillus fumigatus could increase by up to 77 percent by the end of the century. This expansion would include a northward push toward the Arctic, potentially exposing an additional 9 million people in Europe alone to infection risk. Meanwhile, Aspergillus flavus, another harmful species often found on crops, could expand its territory by 16 percent, threatening regions in Russia, north China, Scandinavia, and Alaska.

Professor Elaine Bignell, co-director of the MRC Centre for Medical Mycology at the University of Exeter, said the adaptability of A. fumigatus is partly due to its natural habitat. It thrives in compost piles that can reach high temperatures—conditions that may have enabled it to evolve resilience to the human body’s internal heat. “Its lifestyle in the natural environment may have provided A. fumigatus with the fitness advantage needed to colonise human lungs,” Bignell explained.

Aspergillus: useful in industry, dangerous in health

Despite its danger to human health, not all species of Aspergillus are harmful. Some are used in fermentation processes for products like soy sauce and sake, or in industrial chemistry. But these benefits do not outweigh the growing public health risks associated with environmental and clinical exposure to pathogenic strains.

For most healthy individuals, inhaling Aspergillus spores does not result in illness. However, in people with weakened immune systems—such as those with asthma, cystic fibrosis, or undergoing chemotherapy—the infection can be deadly. Late diagnosis and misidentification remain major barriers to effective treatment, often due to lack of awareness among medical professionals.

Toxic effects of A. flavus on food and health

In addition to health risks, Aspergillus flavus poses a serious threat to food security. The fungus produces aflatoxins, potent toxins that can contaminate staple crops such as corn, peanuts, and tree nuts. These chemicals are linked to liver cancer and acute liver failure. Higher temperatures and elevated carbon dioxide levels, both driven by climate change, are known to increase aflatoxin production.

Professor Darius Armstrong-James of Imperial College London called the potential spread of A. flavus “very worrying.” He noted that outbreaks have already occurred in countries like Denmark and warned that the species may be developing resistance to commonly used fungicides, raising the stakes for agricultural and healthcare sectors alike.

Financial barriers and drug resistance hinder response

Efforts to develop new antifungal drugs have been slow, largely due to the high cost and low profitability associated with these medications. Unlike antibiotics, which treat a broad range of common infections, antifungals often target more specific or rare conditions, making investment less attractive to pharmaceutical companies.

This lack of innovation, combined with increasing drug resistance among fungal strains, is fueling concern among scientists and public health officials. Without effective treatments, even minor infections can become life-threatening, especially for vulnerable populations.

Extreme weather and the rise of fungal pathogens

Extreme weather events—such as wildfires, heatwaves, and intense rainfall—are creating ideal conditions for fungi to thrive and spread. Brittany Bustamante, a scientist at the University of California, Berkeley, said droughts followed by heavy rains can disturb the soil and release fungal spores into the air. Her team is analyzing medical records from over 100 million patients to better understand how environmental factors influence the incidence and severity of fungal diseases.

In recent years, Coccidioides, the fungus responsible for Valley fever, has expanded its range northward from the southwestern United States into Washington State. Like Aspergillus, it thrives in dry, warm conditions and spreads through airborne spores.

Bustamante also highlighted demographic disparities in infection rates. Since 2020, aspergillosis cases have risen most sharply among Latino individuals and residents of rural areas. These increases may be tied to higher exposure to environmental fungi and barriers to healthcare access during the COVID-19 pandemic.

“Given the potential for climate change to drive future respiratory illness surges, secondary fungal infections like aspergillosis are likely to remain a serious public health concern,” Bustamante said. “And the people most at risk will likely be those already facing structural disadvantages and greater exposure to environmental risks like pollution.”

A call for urgent action

As global temperatures continue to rise, so too will the reach and impact of fungal pathogens. The new research on the Aspergillus fungus highlights the urgent need for increased investment in fungal disease research, better diagnostic tools, and the development of new treatments. Without proactive measures, climate-driven fungal infections may evolve into a major global health crisis—one that is already quietly unfolding.