Introduction
Climate change is upending our daily lives with its erratic weather patterns and extreme weather events. While we worry about the very real and visible risks associated with natural catastrophes (uncontrolled fires, heatwaves, flooding, or drought), there is an invisible, but equally worrisome issue emerging from the shifting dynamics of our ecosystems. Fungi, often overlooked in public health and environmental discourse, are quietly adapting to a warming world owing to their ability to survive in diverse environments and adapt rapidly, making them formidable adversaries in a changing climate, and demanding urgent attention.
A Warming World and the Rise of Fungal Pathogens
Climate change is reshaping ecosystems in ways that directly affect human and plant health. Among the most concerning developments is the increasing prevalence and virulence of fungal pathogens. Unlike many bacterial pathogens and viruses, fungi do not require host-to-host transmission. They thrive independently in soil, water, and air, producing vast quantities of spores that can travel long distances. This means that fungi can persist and spread widely without relying on direct contact between hosts, making them harder to control and more likely to cause outbreaks across diverse environments and populations.
Rising global temperatures and altered precipitation patterns linked to climate change are expanding the geographic range of pathogenic fungi. For instance, the emergence of Candida auris, a multidrug-resistant yeast, is believed to be linked to climate adaptation, and it has now spread across every continent[1]. Likewise, fungi from the genus Coccidioides, the fungus responsible for the coccidioidomycosis or Valley Fever (a lung infection), were initially restricted to the arid regions of the southwestern United States, parts of Mexico, and South America. However, warming temperatures and changing precipitation patterns are extending the areas for growth of this fungi. Subsequent dispersal and aerosolization of this pathogen is now extending its range to as far north as Washington State, and is projected to reach Minnesota by the end of the century[2]. Similarly, Cryptococcus gattii, once confined to tropical climates, has emerged in temperate regions like British Columbia and the Pacific Northwest[3]. Another recent study investigating potential climate change-driven geographical shifts highlights how rising temperatures are enabling the spread of Aspergillus fungi into new geographic areas. These fungi are especially dangerous for immunocompromised individuals, like those undergoing chemotherapies or transplant patients and can cause severe respiratory infections for these vulnerable populations[4].
The underpinnings of the climate-driven shift in fungal pathogens
These shifts are not random—they are driven by climate-induced changes in soil composition, rainfall cycles, or even wildlife migration patterns. Worryingly, these shifts are now becoming a global phenomenon. For instance, the expansion of Histoplasma, a soil-dwelling fungus that causes histoplasmosis, has been linked to changes in soil conditions beyond its traditional range in the Ohio and Mississippi River Valleys[5]. Shifting precipitation patterns and drought influence the growth and dispersal of fungi like Coccidioides (as indicated above). Increased rainfall followed by dry conditions promotes spore aerosolization, expanding the fungus’ geographic range. Climate change also affects the movement of birds, bats, and small mammals that act as reservoirs or vectors for fungal pathogens such as Cryptococcus neoformans and Histoplasma. As these animals shift their habitats due to warming temperatures, they may introduce fungi into new ecosystems[6].
The Impact on Human Health: A Growing Burden
Fungal diseases cause a wide spectrum of illnesses In humans, from mild skin infections like pityriasis versicolor (a superficial skin infection caused by Malassezia species)[7] to life-threatening systemic diseases such as invasive aspergillosis. In the United States, fungal infections caused an estimated 7,199 deaths in 2021 alone. To this, one has to add over 75,000 hospitalizations and nearly 9 million outpatient visits[8]. Globally, invasive fungal infections are estimated to affect 6.5 million people annually, contributing to 3.8 million deaths, of which 68% are directly attributable to fungal pathogens[9].
What makes fungal infections particularly dangerous is the lack of effective countermeasures. There are currently no vaccines for fungal diseases, and the arsenal of antifungal drugs remains limited[10]. Resistance to these handful of drugs is rising. Candida auris and Aspergillus fumigatus are prime examples of this issue. The former has rapidly emerged in healthcare settings worldwide and is resistant to multiple classes of antifungal drugs, including azoles, polyenes, and even echinocandins[11], which makes treatment extremely challenging. In the case of A. fumigatus, another common fungal pathogen, it has shown increasing resistance to azole antifungals, particularly in regions with heavy agricultural azole use[12]. This rising resistance is concerning because azoles are a first-line treatment for invasive aspergillosis.
Another issue of concern regarding fungal pathogens is the fact that diagnostic tools remain inadequate for effective and speedy detection, especially in low-resource settings[13]. This diagnostic gap is particularly critical in regions where fungal diseases are most prevalent, such as sub-Saharan Africa, Southeast Asia, and parts of Latin America. In these areas, limited access to laboratory infrastructure, trained personnel, and affordable point-of-care tests leads to delayed or missed diagnoses, contributing to high mortality rates linked to fungal infections. A striking reminder of this was the high incidence of co-fungal infections during the COVID pandemic and the difficulties for their timely diagnosis[14].
Fungi and Food Security: A Double Threat
The direct impact of fungal pathogens extends beyond human pathogenesis. Plant diseases caused by fungi are a major threat to global food security. A malnourished population is even more vulnerable to fungal pathogens. Malnutrition weakens immune defences, making individuals more susceptible to opportunistic fungal infections. This interplay between food insecurity, malnutrition, and fungal disease creates a vicious cycle: crop losses lead to hunger, which increases vulnerability to infection, further straining public health systems, especially in low-resource settings. Moreover, climate change is altering host–pathogen interactions, facilitating the emergence of new fungal strains and increasing the severity of outbreaks.
Globally, plant diseases result in an annual reduction of approximately $220 billion in agricultural productivity[15]. Crop pests and diseases cause 20% to 40% yield losses each year. Historical examples like the Bengal Rice Famine underscore the devastating potential of fungal outbreaks. The Bengal Rice Famine, primarily caused by the brown spot disease in rice, a fungal epidemic of the fungus Bipolaris oryzae, was enabled by unusual weather conditions like heavy rainfall and high humidity. These conditions are now becoming more prevalent with a potentially devastating impact on crop yield.
Recent shifts in fungal species due to warming climates are already affecting staple crops. For example, thermotolerant strains of Puccinia striiformis, the fungus responsible for wheat stripe, are now spreading to warmer regions, causing major outbreaks in the U.S. and Australia[16]. Similarly, Fusarium graminearum, which causes Fusarium head blight, is replacing cooler-climate species and producing more mycotoxins under heat stress, threatening both crop yields and food safety.
Environmental Disasters and Fungal Spread
Climate change is increasing the frequency and intensity of natural disasters—floods, hurricanes, wildfires—that create ideal conditions for fungal proliferation. These events can aerosolize fungal spores, contaminate water supplies, and introduce pathogens into new environments through traumatic injuries or disrupted ecosystems.
For example, a cluster of necrotizing mucormycosis cases was reported following a tornado in Joplin, Missouri. These infections were linked to penetrating trauma from debris contaminated with soil and organic matter. The tornado’s destruction created an environment where fungal spores could enter wounds, leading to severe, sometimes fatal, infections[17]. Flooding from hurricanes and heavy rainfall creates persistently damp environments, ideal for fungi to thrive indoors. For example, after Hurricane Helene in North Carolina, extensive flooding led to widespread mold development in homes and public buildings, raising health concerns for residents, especially those with weakened immune systems. Similar patterns have been observed after Hurricane María in Puerto Rico, where homes with water damage showed increased levels of airborne fungi such as Aspergillus, Penicillium, and Cladosporium[18]. People displaced due to environmental disasters often live in overcrowded, humid conditions that facilitate the spread of dermatophytes like Trichophyton indotineae, which is now showing resistance to antifungal treatments[19].
A Call to Action
Fungi are no longer just decomposers in the forest floor or benign molds on forgotten bread. They are emerging as potent agents of disease, driven by the accelerating pace of climate change. Their rise is silent, often invisible, but the consequences are profound, affecting our health, our food systems, and the integrity of our ecosystems. The growing threat of fungal pathogens in the context of climate change calls for a multi-pronged response. Positive steps in this direction have been seen in the publication of the first Fungal Priority Pathogen List by the World Health Organization (WHO). This list guides global research priorities, surveillance efforts, and funding strategies to combat antifungal resistance and improve diagnostics and has identified 19 fungal species of greatest concern, including Candida auris, Aspergillus fumigatus, and Cryptococcus neoformans[20]. Another initiative in this direction is the launch of a collaborative initiative, the Global Action Fund for Fungal Infections (GAFFI), which aims to accelerate research, surveillance, and innovation in fungal biology and disease management. It supports international partnerships, capacity building in low-resource settings, and the development of new antifungal therapies and diagnostics. The fund also promotes conservation of fungal biodiversity and sustainable use of fungal resources in agriculture and biotechnology[21]. Finally, another example of action is the recent call by the Welcome Trust for projects exploring the mechanisms and triggers for fungal adaptation, particularly in environments that are associated with disease and/or impacted by climate change[22].
The time to act is now. The intersection of climate change and fungal disease is a frontier that demands urgent attention, interdisciplinary collaboration, and sustained investment. By recognizing the threat and mobilizing resources, we can build resilience against this growing challenge and safeguard the health of both people and the planet.
About the Author:
Dr. Pilar Junier is a Swiss-Colombian microbiologist and Full Professor at the University of Neuchâtel, Switzerland, where she leads the Laboratory of Microbiology. With a Ph.D. in Sciences from the University of Chile and a background in genetics from the National University of Colombia, Dr. Junier’s research spans microbial ecology, bacterial-fungal interactions, and environmental microbiology. Originally trained as a bacteriologist, her scientific path took a transformative turn with the discovery of the fungal world, a shift that has profoundly shaped her research and made her a passionate advocate for fungal biology.
Beyond the lab, Dr. Junier is deeply committed to science outreach. She created the award-winning program Microbes go to School, and regularly engages with the public through workshops, school collaborations, and citizen science initiatives. A former President of the Swiss Society for Microbiology and recipient of the Credit Suisse Best Teaching Award, she continues to inspire the next generation of scientists through both her research and her outreach efforts.
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