By Ashley C. Pough, Gwinnett School of Mathematics, Science, and Technology, Lawrenceville, Georgia, USA
Summary
Climate change is contributing to warmer conditions for fungal pathogens to spread into new geographical ranges: better temperatures, more humidity, and more rainfall have favored the expansion of fungal pathogens, and with the rapid occurrence of climate extremes through droughts, flooding, and heat waves—the climate-sensitive fungi are evolving to these changes and new fungi now emerge in higher latitudes becoming more resistant and more adaptable to warmer temperatures which are changing the way scientific and healthcare landscape as newer fungi come to light. The potential spread of fungi may lead to another global health disaster.
Climate change, characterized by progressive global warming, is a significant threat to every ecosystem, affecting plants and animals. A primary concern is the higher likelihood of fungal infections in humans due to the development of thermotolerance in fungi, which enables them to thrive in warmer temperatures giving previously noncommunicable fungi a higher chance of becoming infectious diseases in warm-blooded hosts (Gadre et al., 2022). In some regions, more rainfall and floods lead to more favorable conditions in soil for specific fungi, sometimes infectious fungi, to grow. This increases the likelihood of fungi-related diseases like Chromoblastomycosis (a neglected tropical disease caused by darkly pigmented fungi) and Dermatophytosis (an infection of the hair, skin, and nails caused by mold species like Microsporum, Epidermophyton, or Trichophyton) (Gadre et al., 2022). These fungal infections, caused by temperature and moisture-sensitive fungi, can spread rapidly and introduce themselves to new areas, especially after natural disasters linked to climate change. The increased rate of natural disasters due to climate change heightens the risk of large-scale disruptions of fungal habitats leading to clusters of respiratory, cutaneous, and other forms of fungal spread (Benedict & Park, 2014). The specific examples point to France, which saw an increase in dermatophytosis from 2012 to 2016, when the mean rainfall increased (Gadre et al., 2022). In the opposite extrema, more droughts and arid conditions are correlated to more fungal growth can lead to diseases like Coccidioidomycosis (known as Valley Fever). In Figure 1, the relation to mycology growth and precipitation suggests that as climate change is expected to get worse, this will only heighten the risk of FIs (fungal infections), specifically by 2100, the temperatures are expected to increase by 1.6–6.6°C enabling fungal species linked to Coccidioidomycosis to expand farther north into areas previously unsuitable for their survival (Gorris et al., 2019).
Figure 1: A graph depicting the mean annual temperature and mean annual temperature of the growth of fungi (Expansion of Coccidioidomycosis Endemic Regions in the United States in Response to Climate Change) (Gorris et al., 2019).
Because FIs (fungal infections) impact 1 billion people per year, causing over 150 million severe cases of fungal infections to occur worldwide and 1.7 million deaths per year, unless we are prepared to deal with this likely epidemic, it may be devastating impacts on the healthcare system (Kainz et al., 2020). Physicians currently rely on regional data and current data on common fungal infections to treat FIs. However, the increase in climate-sensitive fungi or fungi previously unknown to infect humans presents challenges in diagnosis and treatment. Consequently, the “at risk” patients who are already immunocompromised and contract fungal infections are likely to pay double the cost, experience longer hospitalization stays, and have an increased risk of death (Rayens & Norris, 2022).
Figure 2: Describes our reliance on both advanced immunity and endothermy to resist fungal pathogens (Casadevall, 2020).
Nevertheless, the human defense against microbial infections relies on two factors: thermal restriction, and advanced immunity, as seen in Figure 2 (Casadevall, 2020). Additionally because about 95% of fungal species are unable to infect humans because of the core temperature, FI would occur more in plants and insects as it has been hypothesized that because of natural selection for fungi that adapt to the warmer temperature, more of which will increase chances of infecting humans. One prime example is the spread of Candida auris, which is thought to have spread to three continents because of global warming.
Other factors increasing the risk of infections with FIs are the growing number of immunocompromised patients with previous diseases (like cancer and AIDS) or older populations. (Kainz et al., 2020). In a study published in the Open Forum for Infectious Diseases, in a study analyzing the hospitalizations in 2018, it found that in the 35.5 million hospitalizations—50.14% of these people had diagnoses associated with a higher rate of FI, and 666,235 people were diagnosed with FIs nevertheless it was found that FIs were underdiagnosed in the at-risk populations (Rayens & Norris, 2022). A solution would be to invest in research to develop newer vaccines and identify potential threats of fungi that may be pathogenetically and destructive (Casadevall, 2020). The escalating number of FIs poses a significant threat to public health with the spread of dangerous and potentially dangerous fungi and the underdiagnosis of FIs in at-risk populations exemplify the urgency to act as we do not want another pathogenic disaster to mimic the disastrous effects of the COVID-19 pandemic.
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