Could a fungus cause a pandemic as the series suggests The last of us Inspired by the video game of the same name? Although this scenario is Unlikely, it’s not entirely impossible, experts argue. And if it should come about the world pharmacopoeia is not prepared for this at all.
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In the hit HBO series, the apocalypse appears in the form of a fungal pandemic: a fungus of the genus Cordyceps has managed to mutate and infect the human brain.
Once infected, legions of this parasite transform into violent, bloodthirsty creatures in just two days. And they’re determined to spread the zombifying fungus by biting — or devouring — their prey.
While this particular Cordyceps strain is fictional, the fungus does exist in the real world. It is even used as a dietary supplement.
However, it only attacks ants and certain insects.
“Cordyceps can induce behavior modification in ants and insects, but not complex zombie behavior over a long period of time, as seen in the HBO series,” specifies the head of mycology at the National Institute Public Health of Quebec (INSPQ ). , Philippe Dufresne.
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And, unfortunately for the imagination, the infection is not transmitted by bite.
“When the ant inhales the microscopic spores of the fungus, about the size of the tip of a needle — the reproductive medium of a mold — the parasite has taken over their body about a month later,” explains Marc Hamilton, president of the Quebec Association of Microbiologists .
“It infects the ant’s motor skills, not their brain,” he continues. She has her whole head, but no longer has control over her movements, which tell her to climb to the top of a branch or leaf, which is the ideal spot for the fungus to reproduce. It eventually comes out of the ant’s body and kills it.”
It was an episode of the 2006 program Planet Earth about the infection of an ant by one of these fungi that inspired the creator of the game The Last of Us, Neil Druckmann, which started in 2013.
Why is a fungal pandemic unlikely?
The video game proposal is original, admit the experts consulted by 24 hours, considering that in the vast majority of post-apocalyptic “pandemic” works, the end of the world is caused by a virus. So original, but not necessarily believable.
First, because pathogenic fungi are not generally transmitted from person to person, according to INSPQ’s Philippe Dufresne.
It is possible to contract a fungal infection from the spores in the air.
Others, called dermatophytosis, which cause nail fungus in particular, can be transmitted through contact with an infected person, animal, or objects. They feed on dead skin, hair and nail tissue.
However, these infections are unlikely to cause the destruction of civilization. Firstly, because they are easy to treat with an antifungal cream. Then because the growth of the fungus is slow compared to that of viruses and bacteria.
“The infection takes several months to develop,” says Mr. Dufresne.
“Fungi are complex and highly developed organisms. Because of this, they don’t undergo the high mutation rate required to take over the human body,” adds Allyson MacLean, biology professor at the University of Ottawa.
So we’re a long way from the ideal scenario for a disaster movie, ironically Marc Hamilton of the Association of Microbiologists of Quebec.
“Cordyceps takes a month to infect an ant, which is a large part of their lifespan. [son espérance de vie varie de quelques semaines et 2 ans], he illustrates. If a fungus were to attack humans, we would have time to find a cure.
Photo: AFP
Another important factor: the temperature of the human body is too high for a fungus to multiply there.
“For a fungus to successfully attack a human, it must be able to tolerate a temperature of [36,6°C]. But most do not survive this temperature. They generally develop between 4°C and 30 or 31°C,” explains Professor Louis Bernier in the Department of Wood and Forest Sciences at Laval University.
A pandemic cannot be ruled out
“Fungi are opportunistic,” said the five specialists surveyed out of 24 hours. Some fungi that have adapted to higher temperatures are therefore able to infect humans, especially those with compromised immune systems.
“A fungal pandemic is a difficult scenario to imagine, except in human populations that would already be in poor health,” argues Tatiana Scorza, a professor in UQAM’s Department of Biological Sciences.
“People who are immunocompromised or already weakened by disease are more susceptible to fungal infections.”
In September 2022, Quebec experienced its first outbreak of Candida auris, a so-called “killer fungus” affecting healthcare patients. An infected person has a 30 to 60% chance of dying.
“For a fungal pandemic to be triggered, it takes the perfect storm: a major event that would have killed a portion of the population and left survivors with weakened immune systems,” explains Louis Bernier.
And should calamity strike that “perfect storm,” it could be very difficult to withstand.
“It’s more difficult to treat fungal infections because, unlike bacteria, there’s less of a difference between humans and fungi,” says biologist Allyson MacLean. Like humans and animals, fungi are formed from eukaryotic cells.
The lack of antifungal medicines could also be an obstacle, Professor Bernier warns.
“There aren’t many products against human fungal infections and we’re seeing more and more resistance. If we see more and more epidemics caused by fungi, the current pharmacopoeia is not sufficiently developed to fight them, unlike bacteria or viruses.