Scientists are usually not too concerned about fungi because after years of evolution, humans have advanced immune systems and high body temperature, which makes it difficult for most fungi to survive. However, a scientist claims that the combination of climate change, medical advancements, and limited antifungal drugs may lead to a fungal infestation similar to the video game “The Last of Us”.
There are more than 300 known pathogenic fungi, the most common being Candida, Aspergillus, and Cryptococcus. Scientists say that humans do not transmit fungi to each other, but spores float in the air and healthy human immune systems are still able to fight them off when inhaled.
Additionally, fungal spores are typically larger than viruses, and masks can prevent infection. Fungi also cannot survive in the human body temperature environment.
However, the situation has changed now. During the pandemic, a drug-resistant and deadly fungus called “Candida auris” spread at an alarming rate in the United States, causing the number of infected individuals to increase rapidly.
The US reported 1,474 clinical cases of fungal infections during the pandemic, nearly a 200% increase from the 500 cases reported in 2019, and nearly half of the patients died within 90 days of infection.
The reason for this increase in fungal infections may be due to the severe damage that COVID-19 and the flu have caused to the human body’s ability to resist fungal infections, leading to an increase in the number of people with weakened immune systems or underlying health conditions over the past three years. Another possible reason is that pathogenic fungi are adapting to warmer temperatures.
Heat stress speeds up fungal gene mutations
A team of molecular genetics and microbiology scientists at Duke University School of Medicine in the United States has found that increasing temperatures lead to accelerated adaptive responses in the pathogenic fungus Cryptococcus neoformans, as reported in the Proceedings of the National Academy of Sciences. During the experiment, scientists witnessed rapid genetic changes in the fungus. Cryptococcus neoformans is a pathogenic fungus that causes meningitis.
The study found that higher temperatures induce more transposons or jumping genes in the fungus, which awaken fungal DNA and cause it to move around, resulting in changes in gene usage and regulation.
After growing on laboratory culture media for 800 generations, the mutation rate of the fungus at 37°C was five times higher than that of the fungus grown at 30°C. This mutation allows the pathogenic fungus to withstand high temperature environments and continue to thrive while infecting hosts.
In summary, heat stress accelerates fungal genetic mutations, resulting in increased heat tolerance or greater disease potential. Researchers are concerned that fungal evolution may be faster than expected.
They also use the popular video game “The Last of Us” as an example, where heat-adapted fungi take over humans and turn them into zombies. Apart from turning people into zombies, anything else is possible in reality.
Molecular microbiology and immunology scientists at The Johns Hopkins University in the United States have stated that this study shows that global warming affects the evolution of fungi in unpredictable ways.
As global temperatures rise, transposons in soil fungi such as the novel Cryptococcus neoformans may become more mobile, causing genes to change in more toxic and drug-resistant directions. This is another concern regarding global warming.