Virology & Mycology
Open Access

Climate Change and the Evolution of Virulent Viral and Fungal Strains

Luka Kovac^{* *}Correspondence: Luka Kovac, Institute of Environmental Microbiology and Pathogen Dynamics, University of Ljubljana, Slovenia, Email:

Author info »

Description

Climate change has emerged as a profound environmental force that is reshaping ecosystems, biodiversity, and pathogen-host interactions across the globe. Among its most concerning consequences is the alteration in the behavior, distribution, and virulence of pathogenic viruses and fungi. Global warming, shifts in humidity, extreme weather patterns, and ecosystem disruption have created favorable conditions for the emergence and spread of infectious diseases, particularly those caused by viral and fungal agents. The intricate relationship between climate and microbial evolution has facilitated the development of more aggressive strains capable of infecting new hosts, expanding into new geographic regions, and resisting traditional therapeutic strategies.

One of the most prominent ways climate change is influencing pathogenic evolution is by modifying the geographic distribution of vectors and reservoirs. Warmer temperatures and altered rainfall patterns are expanding the habitats of insects like mosquitoes and ticks, which are vectors for many viral pathogens such as dengue, chikungunya, and Zika. These viruses are now being reported in areas that were previously non-endemic, bringing susceptible populations into contact with previously unseen diseases. As the virus replicates in new hosts and environments, selective pressure leads to the emergence of more virulent or transmissible variants. For example, arboviruses adapt rapidly to the immune defenses of novel human populations and the physiology of different vector species, leading to evolutionary advantages for more aggressive strains.

Similarly, fungal pathogens are experiencing a parallel evolution driven by rising temperatures. Fungi, traditionally constrained by human body temperature, are beginning to overcome the thermal barrier due to global warming. The emergence of Candida auris is a striking example; believed to have simultaneously appeared in multiple continents, C. auris is resistant to multiple antifungal drugs and survives in warmer environments than most known fungal species. Studies suggest that environmental warming allowed this pathogen to adapt to higher temperatures, enabling it to breach the thermal defenses of mammalian hosts. The same trend is observed in thermotolerant species of Aspergillus and Cryptococcus, which are increasingly reported in climate-stressed zones and immunocompromised hosts.

Beyond temperature shifts, climate change influences fungal and viral virulence through ecological disruption. Deforestation, urban expansion, and habitat fragmentation—often driven by climate-induced human migration—bring humans into closer contact with animal reservoirs and environmental fungal spores. This increased exposure fosters zoonotic spillovers and the transfer of pathogens from animals to humans, sometimes accompanied by mutations that enhance human infectivity. For instance, emerging viral infections such as Nipah and Hendra viruses have been linked to bat-human interactions precipitated by loss of forest cover. Likewise, soil-dwelling fungi like Histoplasma and Coccidioides are finding new territories as wind patterns change and droughts alter soil structure, dispersing spores over greater distances.

Moreover, environmental stressors such as ultraviolet radiation, pollution, and acidification, all linked to climate change, exert additional selective pressures on pathogens. These stressors can trigger genetic mutations, horizontal gene transfer, or epigenetic adaptations that enhance a pathogen’s virulence or resistance to environmental hazards. In viruses, RNA genomes prone to mutation rapidly diversify under these conditions, leading to the emergence of immune-evasive or drug-resistant strains. Fungal pathogens, too, exhibit remarkable genomic plasticity, enabling them to switch phenotypes and become more invasive or drug-resistant in response to environmental cues.

Human and animal health systems are increasingly challenged by this evolving threat. Diagnostic delays, treatment failures, and higher mortality rates are becoming more common in infections caused by novel or resistant strains. Public health preparedness is further complicated by the unpredictability of pathogen evolution and spread. In resource-limited regions, the lack of early warning systems or climate-linked surveillance mechanisms leads to reactive rather than proactive responses, often after significant damage has already occurred.

In conclusion, climate change is not only a driver of environmental degradation but also a catalyst for microbial evolution, leading to the emergence of virulent viral and fungal strains. This phenomenon poses a complex and escalating threat to global health, demanding urgent multidisciplinary attention. Understanding the molecular and ecological mechanisms by which climate shapes pathogen dynamics is essential for developing effective surveillance, prevention, and control strategies. Countries like Slovenia, with diverse ecosystems and increasing climate variability, must invest in climate-resilient health infrastructure, pathogen evolution research, and integrated One Health approaches. Only through coordinated global and local efforts can we hope to anticipate and mitigate the infectious disease risks amplified by our changing climate.