The Last of Us: Could a zombie fungal virus really take over humanity?
Covid was bad, but this could be a whole lot worse.
Scientists in a commonly overlooked field are warning about the growing danger posed by deadly fungal infections, saying the world is not prepared for a pandemic triggered by a nasty fungal disease.
The issue has been thrust into the popular imagination with HBO's hit TV series The Last of Us, adapted from a video game of the same name, in which a fungal virus gets into the global food supply before infecting humans, taking over their bodies and turning them into angry, cannibalistic zombies. The swift collapse of society follows.
Sound far-fetched? Well, not exactly, says Associate Professor Rebecca Drummond who studies immune defence mechanisms against fungal brain infections at the University of Birmingham.
The particular fungus at the centre of the show called Cordyceps is known as the "zombie fungus" for its ability to infect a variety of insects, killing its host before using its body as a puppet for its own needs. Currently, there is no way the fungus could do that to a warm-blooded human – but that doesn't mean never.
The Last of Us: Could it really happen?
“I think the show has a pretty a good scientific premise, but everything is accelerated to what we would see in reality,” Professor Drummond told Yahoo News Australia.
Cordyceps, like most fungi, likes cooler temperatures and can't grow at the human body’s internal temperature of 37 degrees. As the opening scene in the show alludes to, climate change could provide evolutionary pressure for certain fungal species to evolve to thrive in warmer conditions – something that scientists are already beginning to see some evidence of.
Additionally, Cordyceps is no match for a human’s immune response, which is far superior to that of an insect. To get to the point where it could infect our brain and nervous system at the same time would be an evolutionary process that would take thousands of years, Drummond argues.
In The Last of Us, infected humans pass on the virus by biting the next victim. While a perfectly dramatic solution for the show, in reality the transmissibility of such a disease would be very limited.
“Most fungal infections aren't fungal diseases in the sense that if I was infected by a fungal disease, I couldn't give it to someone else. That's partly because you tend to get infected by fungal infections by spores, and fungi tend to produce their spores when they're lacking in nutrients ... and inside of us there's plenty of nutrients,” Drummond explained.
In a comment that sums up much of the show’s premise, she added: “That's not to say that could never happen, but it's quite a big evolutionary jump.”
So while the basic plot is plausible, it’s perhaps something for our great, great, great, great, great, grandkids to start worrying about.
“I don't think it’s something we need to be super concerned about,” Drummond said. But that doesn’t mean researchers aren’t worried about other threats posed by harmful fungal infections.
World 'completely unprepared' for fungal pandemic
Researchers like Dr Neil Stone, leading fungal expert at the Hospital for Tropical Diseases in London, have taken the rare spotlight now on fungal diseases to issue a bleak reality check.
“I think we underestimate fungal infections at our peril,” he told the BBC this week. “We've already done that for too long and we are completely unprepared for dealing with a fungal pandemic.”
It’s a sentiment that Drummond agrees with wholeheartedly.
“I would 100 per cent agree,” she told Yahoo. “The fungal infection field generally has been very under appreciated and under funded, and that’s partly because the impact fungal infections have on global human health has really been underestimated for a very long time.”
But that’s starting to change. Particularly in the wake of outbreaks like the black fungus outbreak in India that has plagued the country's Covid recovery.
In October last year, the World Health Organisation released its first-ever list of fungal pathogens posing the greatest threat to human health, warning that some were becoming more widespread and drug resistant.
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Drummond also points to the fungus Candida auris which is able to withstand temperatures up to 42 degrees and can spread rapidly around hospitals and aged care homes. It causes an infection somewhat similar to sepsis, where the fungus gets into the blood and organs, preventing them from working properly.
“It’s been a particularly interesting fungus, because it appeared on three different continents around the same time,” she said. “And when we did genetic testing on those we realised, they were all independent.
“It’s a fungus that’s everywhere,” she continued, “most fungi are but they don’t bother us because we have intact, normal, healthy immune systems.” But due to factors including the AIDs epidemic, Covid-19 and the widespread use of antibiotics, today “we now have a very large population of people with damaged immune systems – and they are the ones who get fungal infections,” Drummond explained.
Adding to the threat is the inconvenient fact that medical remedies to combat fungal diseases are quite lacking with only a handful of antiviral fungal drugs at our disposal – and Candida auris is already resistant to most of them.
The Last of Us has certainly brought the issue into focus, and for researchers like Professor Drummond, that’s a good thing.
While a vast majority of fungal species aren’t harmful to humans, “on the whole, there’s a lot of the fungal kingdom that we don’t know about,” she said.
“There might well be other potential pathogens out there.”
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