Frightened by fungal zombies in The Last of Us? The real-life threat is terrifying, too

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In HBO’s pilot episode Our LastA scientist on a talk show raises a grim possibility: What if many mind-altering fungi evolved to survive high temperatures in the human body?

“For example, what if the world warmed up a bit?” continued the fictional researcher, to the confusion of the studio audience. “Well, now there’s a reason to evolve.”

This scene opens up the story of the coming apocalypse – a world ravaged by a fungal pathogen that takes over its human hosts, effectively turning them into zombies.

Unfortunately Cordyceps mushroom family To be true, and some have been able to colonize certain insect species, displacing their host tissue and leaving them in a zombie-like state.

Is it possible that one day a fungus could mutate in a way that could take over both our brains and our bodies?

That’s a stretch, scientists say. But the actual evolution of fungi and the real threat these pathogens pose to human health is almost related to science fiction.

“People used to think of fungus as a foot infection, or something trivial, as opposed to a deadly disease. But what we’ve seen is – now people are really paying attention. – fungi are killing more than 1.5 million people each year,” said Leah Cowen, professor of molecular genetics at the University of Toronto and co-director of the mushroom kingdom program at the Canadian Institute for Advanced Research (CIFAR). know.

Many of them, she added, are likely to mutate in the face of climate change, spread to new areas of the world, and become increasingly resistant – all while scientists are Try to diagnose and identify rapidly emerging fungal threats.

“We’re really close to having a silent pandemic,” Cowen said.

Aspergillis mushrooms on a petri dish, harvested from forest soil samples collected at a national park in Calgary. It is one of many fungi that can cause infections in humans. (Kelly Crowe/CBC)

Thousands of fungal threats exist

It has long been known that fungi can change minds and, in some cases, kill their hosts.

Think recreational drugs like magic mushrooms or LSD: Both are derived from mushrooms and both can cause hallucinations or other nasty side effects for the brain.

Then there’s a bunch of life-threatening fungi, including nearly 20 priority pathogens was raised last fall in a report by the World Health Organization (WHO).

One of all, Candida funguswas first detected in the ear of a patient in Japan in 2009.

“And nobody knows what it is,” said Dr. Hatim Sati, technical lead on the WHO final mushroom report. “Fast forward to today, and Candida fungus has been reported in more than 55 countries.”

Capable of causing serious infections, it’s also difficult to identify and is known to cause hospital outbreaks — and some strains are resistant to every currently available drug.

“There are more than 700,000 species of fungi and many of them have everything they need to kill humans successfully,” said Dr. Andrej Spec, a fungal infection researcher and associate professor of medicine at the University of Washington. labour”. of Medicine in St. Louis, Missouri.

Those types of dangerous pathogens, including many rarely seen by the medical community, are often found inside patients who come to his clinic. In a strange case studya fungus known to cause cancer on grasshoppers randomly appeared inside his 78-year-old patient’s knee, causing mysterious pain and swelling for months before the man finally diagnosed.

For more vulnerable people, including those who are immunocompromised or have diseases such as cancer, infections are more likely to become deadly. There are also countless unknown fungal threats lurking around the world, which can affect plants and insects, but not humans — at least not yet.

The relationship between temperature, the evolution of fungi

“The main difference between them and the fungi that make us sick is that they are not tolerant of our body temperature. [of 37 C]”Spec said.

As the climate warms and the world experiences more extreme weather events, that “changes the evolutionary path of these fungi to become more heat-tolerant,” he added.

Spec .’s own researchpublished last winter in the journal Clinical Infectious Diseases, shows that certain fungi once thought to have been confirmed in certain parts of the US are now much more widespread – while another study in Chronicle of internal medicine found more than 10 percent of currently diagnosed fungal infections outside of areas where such threats were known to be endemic.

“I think we’re also going to see a lot of unusual fungi emerge over the next few decades, the kinds of fungi that we’re going to see,” said Dr. George Thompson, one of the authors, and a researcher at the University of California-Davis. We usually don’t see the infection in the patient.” “I think climate change is going to play a role in that.”

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A new sheet of paper, out this week in PNAS . magazinepushes theories around fungi and climate change one step further, by assessing the effects of heat on a species in the laboratory.

Duke University research team studied fungal pathogens in humans code — a “major killer,” said researcher Asiya Gusa — and evaluated its genome under different conditions.

Gusa told CBC News: “We found that genetic changes in fungi occur more rapidly when cells grow under heat stress.

Although the laboratory context does not apply directly to the real world, Cowen of the University of Toronto – who was not involved in the study – said the study provides a glimpse into potential mechanisms. in allowing fungi to grow in a way that in some cases can pose a greater threat to human health.

“If heat stress acts as a trigger for mutational adaptation, this could happen faster than we anticipated which is a bit scary,” said Gusa.

Fungal infections are still difficult to treat

Also worrying, the scientists say, is that fungal infections are difficult to treat.

That’s largely because fungi and humans have more in common than you might think. Both are eukaryotes, which are part of many species — including all animals and plants — whose cells contain a nucleus and a variety of other components that perform different functions.

In contrast, viruses are not cellular organisms at all, which means that medical treatments are targeting an entirely different kind of threat.

But when you’re trying to target a fungus while it’s living inside a human host, things get complicated.

“The problem is that most antifungals are also pretty good anti-human agents,” explains Spec. “And it’s a balancing act to find a drug that kills the fungus, but doesn’t kill the patient.”

As more fungi become resistant to drugs against them and their global reach increases, scientists fear that we are reaching a tipping point when fungal pathogens will have an increasingly large impact on human health. human health – no need for zombies on television.

Leah Cowen, professor of molecular genetics at the University of Toronto and co-director of the mushroom kingdom program at the Canadian Institute for Advanced Research (CIFAR), says mushrooms are killing more than 1.5 million people each year.
Leah Cowen, professor of molecular genetics at the University of Toronto and co-director of the mushroom kingdom program at the Canadian Institute for Advanced Research (CIFAR), says mushrooms are killing more than 1.5 million people each year. (Lauren Pelley/CBC)

The fact is that fungi already have the ability to thrive in many environments. Fungal spores can survive in soil, inside hospital ducts, or in people’s homes, and different forms of fungus can also colonize human skin. Mold even grows in the International Space Stationaway from their typical environment on earth.

“Mushrooms are mobile, many of which are dispersed by spores, and they are very airborne and moving around,” Cowen said.

That means if the world sees a proliferation of a highly infectious fungus, the protective measures used against other pathogens may not be effective. newspaper.

“Outside, you’re not safe. Inside, you’re not safe. If you have a HEPA filter, you’re not safe either,” he said. “In the ‘Bubble Boy’ rooms, they still have fungal infections there. And so it’s impossible to prevent the fungus in the environment. So that’s the really scary part.”

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Pandemic risk

So fungi have pandemic potential? Probably didn’t like the dire scenes in Our Last.

But the answer is still “yes,” said Dr. Arturo Casadevall, a professor of microbiology at the Johns Hopkins Bloomberg School of Public Health and a longtime researcher on fungal threats.

Although there have been no recorded outbreaks of a fungal pandemic affecting humans, other animals, including frogs, have been ravaged by several fungi. A species of bat from the United States has also been pushed to the brink of extinction by white nose syndrome, a fungal disease. So it’s not ruled out that something similar will happen to us, says Casadevall.

“Just because it doesn’t happen, doesn’t mean it can’t happen,” he added. “When I was in medical school, at first, retroviruses weren’t considered a human pathogen – and HIV caused us a pandemic. And when I went to medical school, the coronavirus was thought to cause colds in people. you… now we have SARS, MERS and the pandemic of 2019.”

It’s all rooted in reality — not TV shows or video games.

“We need to care [about] Casadevall said. “And just because they haven’t happened doesn’t mean complacent.”


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