What if COVID-19 wasn't the disease to plunge the world into a pandemic?
What if it was a parasitic fungus?
One that, under the right conditions, can mutate, infect and kill humans?
That is the chilling premise of HBO's The Last of Us: a post-pandemic world devastated by a mass outbreak of a "zombie fungus" that infects and takes over the mind of its hosts.
But it's fiction, right?
Not really — zombie fungus does exist
The creators of The Last of Us video game have said they were inspired by an episode of BBC's Planet Earth series, narrated by David Attenborough.
The episode shows an ant infected with a fungus that hijacks its brain, virtually bending it to its will.
Forcing the ant to climb a tree and dangle above the forest floor, the fungus digests the ant’s body from the inside out and unleashes a shower of spores to create more "zombies".
Enter: David Hughes from Penn State University in Pennsylvania.
He's one of the world's leading experts in this subject who consulted on the video game.
"The original BBC Documentary called it Cordyceps — but correctly, we should say Ophiocordyceps," Professor Hughes told ABC News.
"Cordyceps and Ophiocordyceps are related fungi."
When asked how many species of Ophiocordyceps there were, Professor Hughes said, "likely thousands".
So out of this number, how many can infect and perform "mind control" on their hosts?
Can fungi infect and control humans?
Infect, yes.
Control, no.
*Sigh of relief*
"It’s not possible in the way The Last of Us shows us," says Justin Beardsley, an infectious diseases researcher at the University of Sydney.
Most species of parasitic Ophiocordyceps have evolved over millions of years to specialise in infecting only insect species — mainly ants and wasps.
"For this fungus to be able to jump from an insect and into humans and cause an infection is a very big leap," he said.
Professor Hughes echoes this, saying our nervous systems are far too different for a parasite to manipulate our minds.
But both scientists warn there are life-threatening ways fungi can affect us.
Can fungi kill humans?
Some can.
"If people eat toxic fungi, they may experience digestive problems, hallucinations, organ failure, and even death," Professor Hughes said.
The scary part is that most cases of mushroom poisoning are due to mistaken identity.
"That's because many toxic mushrooms look very similar to safe, edible mushrooms," Dr Beardsley said.
"But there is no evidence of them infecting humans or any other animals, and controlling their behaviour."
Could climate change increase the chances of a scenario from The Last of Us?
One of the shows most chilling moments is in its opening scene: a talk show conversation with two scientists in 1968.
It's this moment when the show declares the real cause of the spread of Ophiocordyceps infections to humans: climate change.
"This is a realistic proposition and might already be happening," says Ana Traven, a professor of biochemistry and molecular biology at Monash University.
Professor Traven uses the example of Candida auris: "a fungus which causes life-threatening human infections that are difficult to treat," she said.
"The human body is too warm for this fungus.
"But warmer temperatures due to climate change might cause this fungus to adapt — to grow at human body temperature (37C)."
Professor Traven says this sort of adaptation can cause a normally benign fungus to become "a serious human infection".
"This is a genuine concern in infectious disease and medical mycology circles," Dr Beardsley said.
"As temperatures rise, fungi will adapt to survive at temperatures very close to our own, making infection possible."
Fungi are the 'forgotten' infectious disease
In October 2022, a list of 19 fungi representing the greatest threat to human health was released by the World Health Organization (WHO), with a warning some strains are increasingly drug-resistant and becoming more widespread.
"Fungi are the 'forgotten' infectious disease," Dr Beardsley said.
"They cause devastating illnesses but have been neglected so long that we barely understand the size of the problem."
Currently, fungal infections receive less than 1.5 per cent of all infectious-disease research funding, according to the report based on research led by the University of Sydney.
Worldwide, fungal infections kill 1.7 million people each year, more than malaria.
Human bites could spread fungus: fact or fiction?
You'll be glad to know all three scientists called fiction on this.
"Definitely not as depicted in the show," Dr Beardsley said.
He explains that many fungal infections are spread by inoculation – meaning they need something to break the skin to cause an infection.
"So if there was a fungus living in the biter’s mouth, that would be a way for it to get in," he said.
The Last of Us is helping people 'take fungal infections more seriously'
The three scientists said they are indeed watching (and loving) the show.
Professor Hughes feels "excited" seeing something he contributed his expertise to, flourish into a worldwide hit.
"My daughter Chiara and niece Cassie played the game, so it's been amazing to now watch the show with them," he said.
"It's great to have some coverage of the potential risk fungi present to us," Dr Beardsley said.
"Those risks are huge in terms of infections, risks to food security and risks to biodiversity. But not so much for zombie apocalypses."
Professor Traven said she is "intrigued" at how much media attention the show has generated.
"It's a good thing!" she said.
"We need to start taking fungal infections more seriously, and invest research efforts and funding into finding new antifungal therapies."
