Could a deadly fungus really cause a pandemic? : Goats and Soda : NPR

The premise of The last of us is that the cordyceps fungus turns people into creatures that obey the fungus.

HBO Max/Screenshot by NPR

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HBO Max/Screenshot by NPR

The premise of The last of us is that the cordyceps fungus turns people into creatures that obey the fungus.

HBO Max/Screenshot by NPR

From a scientific point of view, the new HBO show The last of us a whopper tells us – a mesmerizing whopper.

In the show, climate change has fueled the rise of a new pathogen, which is sweeping the globe infecting humans, turning them into zombies and controlling their brains.

The cause of the infection, however, is a bit surprising. “Not bacteria? Not viruses?” a TV reporter asks a scientist in front of a live audience during the first episode.

“Mushroom”, replies the scientist. The audience laughs.

“Yes, that’s the usual answer,” says the scientist.

And then he goes on to explain why fungi are a serious threat to humanity, underscoring the idea that rising temperatures on Earth will make them more infectious to humans.

When I watched this scene, I have to admit I laughed out loud too. “A fungus wiping out humanity? Come on.” I thought. “It’s not even a remote possibility.”

But then, for this story, I started researching the possibility of a fungus triggering a pandemic, and I have to admit I was wrong. I shouldn’t have laughed – not even a little bit. Because there’s growing evidence — real evidence — that climate change may actually make this class of pathogens more dangerous to humans.

Viruses vs Fungi? What is the greatest danger for humanity?

For the past decade, I have reported on infectious diseases. I’ve often asked scientists, “What keeps you up at night?” What kinds of pathogens could cause a horrible pandemic? Each time, I heard one type of pathogen over and over again: viruses. The specific family of viruses that scientists are concerned about varies, but they are usually the flu, a SARS-like coronavirus, or a paramyxovirus (which causes horrific illnesses such as nipa And Hendra).

No one ever said “mushrooms” in response to my query. And a fungus has never caused a massive pandemic, similar to what the world is experiencing with COVID-19. The reason? Viruses have several great advantages over fungi when it comes to infecting people. For starters, they spread much faster.

“So the big advantage, if you will, for viruses is that one virus particle can become thousands of particles in a very short time,” says Dr. Aileen Maria Martywho is an infectious disease specialist at Florida International University and has worked with the World Health Organization on several recent outbreaks, including Ebola in West Africa in 2014 and Zika in 2016.

“Besides,” Marty said, “like [the virus] produces more viral particles, it has the propensity to have mutations.”

This tendency to mutate means that viruses can change and evolve much faster than fungi. “These mutations can lead to a new version that could be more dangerous quickly,” says Marty. So all of a sudden, say in a few weeks, the virus can start evading people’s immune systems. Then, in a flash, the whole world becomes susceptible to the virus again, as we experienced with omicron and its countless variants.

Here’s the key thing: mushrooms usually can’t do this, studies showed. They mutate about 10,000 times slower than viruses, on average, scientists say. (The exact estimate depends on the specific virus and fungus.)

Plus, Marty points out, people with a healthy immune system can fight off fungal infections before they become dangerous. “The reality is that most immunocompetent people don’t get sick from a fungus that enters their body.” The same cannot be said for many viruses.

So I ask Marty, “If you had to put money on what’s going to cause the next pandemic, would you put it on a fungus or a virus?”

“I would put it on a virus. I really would,” she says without hesitation. “But that doesn’t mean we shouldn’t pay attention to fungi because many, many, many, many people die from fungal infections every year.” In fact, more than 1.6 million people die each year from fungal infections. And there are growing fears that those deaths are increasing, in part because of climate change.

Fungi are changing and could become more contagious to people

So here’s where the show The last of us gets the science right – or at least partially right. Most fungi live in the terrestrial environment, such as in soil and on plants. They can’t survive in humans because humans get too hot, says Laura Bonmanwho studies pathogen genomics at Cornell University.

But like the scientist in the first episode of The last of us explains: “Currently, there is no reason for fungi to evolve to be able to withstand higher temperatures. But what if that were to change? What if, for example, the world were to warm up slightly? … Well, now there is [a] why fungi evolve.

In other words, could climate change cause fungi to survive higher temperatures, like that of the human body, making them more capable of infecting humans?

There is evidence that this process is already underway, at least with one species of fungus, called white ears. It is an emergent species, detected for the first time in the ear of a 70-year-old woman in Japan in 2009, and it has already appeared independently on three continents.

A researcher holds a Petri dish with Candida auris in a lab at the University of Wuerzburg in 2018.

Nicolas Armer/picture alliance via Getty Image

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Nicolas Armer/picture alliance via Getty Image

“This species of fungus is quite unpleasant,” Goodman says, “because it is resistant to many drugs that we have.

“And not only that, it also seems to have a strong advantage in changing in such a way that it can cause illness in people.”

Studies suggest C. ear can mutate as quickly as some viruses, and rising temperatures in some parts of the world may have caused it to survive higher temperatures, possibly giving it the ability to infect people .

Right away, C. ear is a major problem in many hospitals, including those in the United States, Goodman says. But it is especially a risk for people whose immune system is compromised and who are very ill. “For a lot of people, it’s probably harmless.”

She fears that will change.

“Fungal infections definitely keep me awake at night,” she says, “because I see all the work that’s being done on bacteria and viruses and all the stuff we know about all those microorganisms. And then we look at fungal pathogens, and I see we know a lot less.”

And, while no fungus has caused deadly pandemics in humans, they have caused horrific outbreaks in wildlife.

“All you have to do is watch bats with white nose syndrome or frogs and salamanders with chytrid mushroom“, she says. “These fungi are really devastating pathogens for these species, capable of essentially eliminating whole groups of these wild animals.

So it turns out the writers of the HBO show understood more science than I thought. But rest assured, there is no current evidence of fungi on the horizon that will infect our brains and control our minds.