The new HBO series “The Last of US” presents a post-apocalyptic scenario where thousands of people are turned into zombies after a fungal infection becomes a pandemic. The series was the second biggest premiere this year on the HBO MAX platform and the third episode is available this Sunday (29).
The scenario may be fanciful, but the kind of mushroom depicted in the series really exists. They are fungi of the genera Cordyceps and Ophiocordyceps and in real life turn their victims into zombies.
The spores of this type of mushroom enter the victim’s body, where the mushroom grows and begins to hijack its host’s mind until it loses control and is forced to ascend to higher ground. The parasitic fungus devours its victim from the inside out, extracting every last nutrient as it prepares for its grand final deed.
Then – in a creepier scene than the scariest horror movie – a death tentacle erupts from the head. This mushroom body spreads spores all around itself, dooming other victims to the same fate if they are too close to be infected.
Fortunately for us, fungi of this genus are only capable of infecting ants and only a few species. Other similar fungi contaminate other insect species in a similar way. This BBC documentary shows an ant infected with the fungus:
How these parasitic fungi worked inspired the video game The Last of US, on which the HBO series was based.
In the plot of these works of fiction, Cordyceps fungi become capable of infecting humans and causing a pandemic capable of leading to the collapse of society.
But in the real world, could a Cordyceps pandemic — or one caused by another fungus — actually happen?
“I think we underestimate fungal infections at our peril,” says Dr. Neil Stone, the principal fungal expert at the Hospital for Tropical Diseases in London. “We’ve been doing this for too long and are completely unprepared for a fungal pandemic.”
List of mushrooms dangerous to humans
At the end of October last year, the World Health Organization (WHO) released its first list of mushrooms with the highest risk to public health.
The mushrooms on the list are indeed menacing, but – to our relief – none on the list are capable of turning humans into zombies.
Microbiologist Charissa de Bekker of Utrecht University in the UK studies how Cordyceps fungi zombify ants and says she doesn’t see how that could happen to people.
“Our body temperature is just too high for most fungi, including Cordyceps,” she explains. “Their nervous system is simpler than ours, so it’s much easier to hijack an insect’s brain than the complex human brain.”
Also, he explains, their immune systems are very different from ours, which would make this “seizure” difficult as well.
Most parasitic Cordyceps species have evolved over thousands of years to specialize in infecting only one insect species. Most don’t jump from one insect to another.
“For this fungus to jump from an insect to us and be able to infect us the same way, that’s a very long distance,” says Bekker.
However, the threat of a fungal pandemic is very real, although it has long been underestimated. “People think of mushrooms as something trivial, superficial, or unimportant,” says Dr. Neil Stone.
Only a few of the millions of species of fungi cause disease in humans. However, some of these can be much worse than an infected toenail or chilblain.
Fungi kill about 1.7 million people a year, about three times as many as malaria.
WHO has identified 19 different fungi that it considers of concern.
The most serious are Candida auris, Cryptococcus neoformans and Mucormycetes, which gobble up our flesh so fast that they cause severe facial injuries.
The global threat of candida auris
THE candida auris it’s a yeast – and gives off the same fermented smell as a brewery or bread dough.
But unlike the beneficial yeasts we use for food, candida auris it is a terrible parasite.
It contaminates the blood, nervous system and internal organs. WHO estimates that half of people infected with candida auris to die.
The first documented case was in the ear of a patient at Tokyo Metropolitan Geriatric Hospital in 2009, and the fungus has since spread around the world.
THE candida auris it is very difficult to fight – some strains are resistant to all the antifungal drugs we have. For this reason it is often called a “super mushroom”.
Transmission is mostly through contaminated surfaces in hospitals – it’s a really hard fungus to clean up completely. Often the solution is to close entire hospital wards, which has already happened in the UK.
Neil Stone says the candida auris it is the most worrying type of fungus and we cannot ignore it, as a pandemic caused by it could lead to the collapse of health systems.
Another deadly mushroom – the Cryptococcus neoformans – is capable of entering the nervous system of people and causing devastating meningitis.
Brits Sid and Ellie came across the disease in the early days of their honeymoon in Costa Rica. Elle began to feel sick, and her initial symptoms — headache and nausea — were attributed to too much sun. But then she started having very strong spasms and convulsions.
“I’ve never seen anything worse, I felt so helpless,” Sid tells the BBC.
Tests carried out showed inflammation in his brain and identified cryptococcus as the cause. Fortunately, Ellie responded to the treatment and came out of the coma after 12 days of ventilation.
“I just remember screaming,” she says, who had delusions when she was infected.
Now he is recovering well.
Ellie says she “never” thought a mushroom could do this to a person. “You don’t think you are going to die on your honeymoon.”
Another public health threat is Mucormycetes, also known as black fungus. It causes a very serious disease called mucormycosis, which usually affects people with compromised immune systems.
It reproduces so rapidly that, when grown in the laboratory, it can blow off the lid of a petri dish.
“When you let fruit go bad and it turns to mush the next day, it’s because there was a mucomycete fungus inside it,” says Dr Rebecca Gorton, a scientist at HSL, the London Health Services Laboratory.
He says the infection is rare in humans, but it can be really serious when it happens.
The fungus attacks the face, eyes and brain and can be fatal or leave people severely disfigured. An infection spreads as quickly in the body as it does in fruit or in the lab, Gorton says.
During the Covid-19 pandemic, there has been an explosion of black fungus cases in India. More than 4,000 people died. People’s weakened immune systems and high levels of diabetes in the country are thought to have contributed to the mushroom’s proliferation. In 2021, about 30 cases of mucormycosis contamination were recorded in Brazil.
Should we take mushrooms more seriously?
Fungi generate infections that are very different from those caused by bacteria or viruses. When a fungus makes us ill, it is almost always picked up from the environment rather than spread through coughs and sneezes.
We are all constantly exposed to fungi, but they usually need a weakened immune system to thrive.
Stone says a fungal pandemic would likely be very different from the Covid pandemic, both in how it spreads and the kinds of people it infects.
He thinks the threat exists because of the “volume of fungi that exist in the environment” and “climate change, international travel, the growing number of cases and the profound disregard we have in terms of treatments.”
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