Climate Change Is Supercharging Deadly Fungal Infections and We’re Not Ready

Fungal infections rarely make headlines the way viral pandemics do, but a new chapter published in the Springer volume Global Health, Climate Change, and Emerging Infectious Diseases makes a compelling case that they should. Authored by Daniel B. Chastain, Mary E. George, David B. Cluck, and Andrés F. Henao-Martínez, the review argues that climate change is systematically rewriting the ecological and evolutionary rules that once kept dangerous fungi in check, with consequences that are already showing up in emergency rooms and ICUs.

Rising Temperatures Are Selecting for More Dangerous Fungal Pathogens

Heat is not just uncomfortable for fungi; it is a filter. Species that cannot survive near mammalian core body temperature (around 37°C) are naturally excluded from causing human disease. As global temperatures rise, that thermal barrier is eroding. The chapter details how heat stress activates a suite of survival machinery in fungi: heat-shock protein networks, calcineurin signaling, protein kinase A pathways, and membrane remodeling systems that maintain fluidity at higher temperatures. Antioxidant defenses ramp up. In some species, elevated temperatures even trigger morphologic switching, a shift between growth forms that tends to correlate with increased virulence.

The most striking illustration of this process is Candidozyma auris, formerly known as Candida auris. This thermotolerant species emerged nearly simultaneously on multiple continents over the past two decades, spread rapidly through healthcare settings, and has accumulated resistance to multiple antifungal drug classes. The authors treat it as a proof-of-concept for climate-linked pathogen evolution: a fungus adapted to survive at body temperature, persist on surfaces and skin, and resist treatment. Broader research on how climate change drives fungal pathogen emergence confirms this pattern is not unique to C. auris; thermotolerance is becoming a recurring theme across multiple genera.

Endemic Mycoses Are Expanding Into Unexpected Regions

For decades, clinicians in the northeastern United States or northern Europe could reasonably treat a diagnosis of Valley fever (caused by Coccidioides species) or histoplasmosis as a travel medicine question. That assumption is becoming unreliable. The chapter documents range expansions for Coccidioides, Blastomyces, and Histoplasma species tied to shifts in precipitation, soil moisture, and temperature that alter where these organisms can survive and sporulate. When soils dry after wet periods, wind aerosolizes spores; when those weather cycles intensify, so does exposure.

The scale of the projected shift is substantial. Climate niche modeling predicts that by 2100, the endemic area for Valley fever in the United States could more than double, expanding into states previously considered non-endemic and increasing case counts by roughly 50%, with agricultural regions particularly affected. Clinicians practicing far from the traditional endemic Southwest may increasingly encounter patients with pulmonary infiltrates, fever, and a history of outdoor exposure who have never left their home state. Missing these diagnoses delays treatment and inflates mortality.

Extreme weather events add another vector. Dust storms, wildfires, floods, hurricanes, earthquakes, and tornadoes disturb fungal reservoirs, launch spores over long distances, contaminate built environments, and increase infection risk through both inhalational and cutaneous routes. Trauma wounds sustained during disasters and near-drowning events are particularly associated with cutaneous and invasive fungal infections, especially when healthcare infrastructure is simultaneously compromised.

Agricultural Azole Use Is Accelerating Drug Resistance in Aspergillus and Candida

One of the chapter's most clinically urgent points concerns antifungal resistance, and it originates not in hospitals but on farms. Azole fungicides, used extensively in agriculture to protect crops, share a structural and mechanistic similarity with medical triazole antifungals such as voriconazole and itraconazole. Years of field application have imposed persistent selection pressure on environmental fungal populations, particularly Aspergillus fumigatus, the leading cause of invasive mold infection in immunocompromised patients.

The result is a growing population of azole-resistant A. fumigatus strains in the environment, carrying resistance mutations (notably in the cyp51A gene) that are identical to those found in clinical isolates from patients who have never received antifungal therapy. The authors note that temperature and fungicide exposure may interact synergistically, meaning climate warming does not simply add to resistance pressure; it may multiply it. Similar dynamics are playing out in Candida species and Cryptococcus species, where environmental selection is shifting susceptibility profiles and, in some cases, influencing virulence. Research tracking climate change's impact on fungal distribution and virulence links these resistance trends directly to increased morbidity and mortality in clinical settings.

Diagnostic Gaps and Social Determinants Deepen the Crisis

Even when a clinician suspects a fungal infection, confirming the diagnosis quickly is hard. Most invasive fungal infections still require culture, which is slow; Coccidioides in particular requires biosafety precautions that limit where cultures can be processed. Non-culture diagnostics, including antigen tests and beta-glucan assays, exist but have variable sensitivity depending on the species and patient population. For newly expanding pathogens appearing in non-endemic regions, laboratory staff may not think to order the right tests or interpret unexpected results correctly.

The chapter stresses that social determinants of health compound exposure and worsen outcomes. Agricultural workers, people experiencing homelessness, and communities with limited access to healthcare face both higher environmental exposure and greater diagnostic delays. PLOS Pathogens has noted that distinguishing climate-driven range shifts from other factors remains methodologically difficult, partly because surveillance infrastructure in low-resource settings is thin. That gap in data makes it harder to allocate diagnostic resources, update treatment guidelines, or justify investment in new antifungals.

A One Health Framework for Fungal Disease Surveillance and Prevention

Chastain and colleagues argue that no single-sector response is adequate. What they call a One Health agenda would integrate sustainable agricultural practices to reduce environmental azole loading, resistance monitoring in both clinical and environmental isolates, expanded epidemiological surveillance that can detect geographic shifts in real time, and equitable access to diagnostics and antifungal treatments. Berkeley Public Health has launched a major study linking climate, socioeconomic data, and fungal disease outcomes to identify high-risk areas and develop predictive tools, the kind of infrastructure the chapter's authors are calling for at scale.

On the therapeutic side, the pipeline for novel antifungals has historically been thin relative to antibacterials, but the review points to host-directed strategies and vaccine development as promising directions. For practicing clinicians, the near-term message is more immediately actionable: broaden the differential to include thermotolerant or geographically unexpected fungal diagnoses, factor environmental and occupational history into workup, and treat antifungal stewardship with the same seriousness now applied to antibiotics. The fungi are adapting. Clinical thinking needs to keep pace.