Question: Did you inhale fungal spores today?
Answer: Yes. Absolutely. Tons of them. It’s everywhere.
“Anyone who’s outside has inhaled fungal spores,” says Vincent Bruno, a scientist at the University of Maryland School of Medicine’s Institute for Genome Sciences who researches fungal diseases. Luckily, though, your mind wasn’t infected by the Cordyceps fungus, which in the HBO series The last of us leading to a global outbreak that transforms the unfortunate infected into vicious zombie-like characters who will spread disease to the dwindling (and often desperately hungry) human population.
Such a fungal infection in humans is magical fiction. However, in reality, Cordyceps regularly teases the mind of a species of ants(Opens in a new tab). The fungus cleverly forces the ants to climb into favorable environments for the fungus to grow. “It turns them into zombies,” Theresa Gildner, a biological anthropologist at Washington University in St. Louis who researches parasitic diseases, told Mashable. The Cordyceps then boldly emerges from the ant’s head, allowing the spores to spread to other unwitting ant hosts. Indeed, nature can be wild. This very fungal ferocity in ants inspired The last of us video game that led to the popular new series starring Bella Ramsey and Pedro Pascal.
Importantly, although some fungal spores can cause serious human infections under certain circumstances, a mind-controlling fungal parasite is thankfully not in the cards. Here’s why.
People are still eating bread in ‘The Last of Us’ and I don’t understand why
The parasitic fungus Cordyceps grows from an infected ant.
Credit: Reza Saputra/iStock/Getty Images
Why the Cordyceps fungus will not infect humans
When you take a walk in the forest, it is the world of fungi. we just get through it. Organisms feed on dead creatures, recycling bodies, and organic matter in the soil while forming vast underground networks(Opens in a new tab). They thrive in the natural world. There is nothing to stop them.
“In the world, there’s no immune system that’s trying to kill them,” Bruno told Mashable.
“Humans are really, really good at preventing fungal infections.”
But herein lies a problem for most fungi. They can rarely survive in the human body. “Humans are really, really good at preventing fungal infections,” Bruno pointed out. There are three strong reasons why:
Advanced Immune System: Our immune system is much more complex than an ant’s – and a fungus can’t overcome our layered defenses. “Our immune system recruits white blood cells to come and kill it,” Bruno pointed out.
We are endothermic: This means we are warm-blooded. Many fungi cannot survive in such hot environments.
Enhanced immune system: Microbes thrive inside the human gut, including some fungi. This allows our immune system to recognize and differentiate between normal fungi and fungal invaders found in nature. Our immune system is primed to attack foreign, potentially harmful, spores.
A shot of a fungus-infected character in “The Last of Us.”
How some fungi cause serious diseases in humans
Humans, however, are not completely out of the fungal forest. Certain fungi can seriously infect us when we are weak.
“In order to fight off a fungal infection, there has to be something wrong with your immune system,” explained Dr. Luis Ostrosky, MD, a fungal infection specialist and professor of infectious diseases at UTHealth Houston. He is also chief of epidemiology at Memorial Hermann Academic Hospital.
Compared to 30 years ago, these types of fungal infections are much more common, he noted. And this is because modern medicine necessarily allows for more and different types of immunocompromised patients. These include people who have undergone organ transplants or other major, life-saving surgery that was not possible in the past, as well as people who have undergone cancer treatments. “We’re creating a paradigm shift in the number of people who are immunocompromised,” Dr. Ostrosky said. It is important that infectious disease doctors know how to recognize and treat such diseases(Opens in a new tab).
In hospitals, one of the most commonly encountered fungal infections, with approximately 25,000 cases in the US annually, is Candida. Candida is everywhere and our immune system keeps it in check. But for those with weakened immune systems, Candida can cause a serious blood infection. Even worse, a strain called Candida auris(Opens in a new tab) has emerged in recent years. It can be resistant to some, or all, antifungal drugs and has caused outbreaks in hospitals, Dr. Ostrosky noted. “Candida auris is an emerging fungus that presents a serious global health threat,” says the CDC(Opens in a new tab). Then there’s Aspergillus — a mold we all breathe every day. But for those undergoing chemotherapy or taking immunosuppressants, the common fungus can be serious. “We used to see it once a month,” explained Dr. Ostroski. “Now we see it once a day. It’s one of the deadliest fungal infections.”
Harmful fungal spores can easily spread outside the hospital. Valley fever(Opens in a new tab) it is caused by the fungus Coccidioides, which thrives in hot and dry soils, such as in the Southwest. People breathe it in and some people are vulnerable(Opens in a new tab). Valley fever is now showing up in new places like Washington state and Chicago. This could be the product of the relentlessly warming climate leading to new places for Coccidioides to thrive(Opens in a new tab)Dr. Ostroski said.
This may also be a possible harbinger of future, potentially alarming valley fever scenarios in dry or drought-affected regions. “Imagine spores being blown across the country,” thought Dr. Ostrosky. “This is a more likely scenario than zombies caused by fungi.”
In nature, mind-controlling parasites are very real
Although human infection in The last of us Not true, in the wider animal kingdom and beyond, parasites regularly alter the minds of their unwitting hosts. To them, a mind-controlling scourge is no enticing fiction.
“There are so many scary, but interesting examples,” said Gildner, the biological anthropologist.
“There are so many scary, but interesting examples.”
Worm-infected ants infect grazers: A parasitic worm (Dicrocoelium dendriticum) affects the ants’ brains, prompting them to climb to the top of a blade of grass at night instead of returning to their colony, Gildner explained. This increases the chances that a grazing animal – which the worms seek to infect – will eat the ants. “That’s the ultimate goal of the parasite, to get inside a grazing animal so it can complete its life cycle and reproduce, and it’s just one example of how many species of parasites manipulate their hosts to achieve a very specific goal. Gildner said.
Brain-infected crickets: The extremely minute horsehair maggots infest crickets and other insects. For example, in caves such as those in Carlsbad Caverns National Park, crickets take a sip of water and suck up the young worms. The worms grow inside the cricket, consume the cricket’s body and eventually make contact with the brain(Opens in a new tab). They probably release mind-altering chemicals into the cricket’s brain. Finally, the crickets, who doesn’t know how to swimthey are forced to jump into the water, allowing the fully grown worm to emerge…and reproduce.
Insidious parasite in cats: The parasitic microbe Toxoplasma gondii has adopted a clever way of infecting cats. It reproduces in cats and is then excreted in the cat’s feces. Rodents eat poop, and always the germ, too. Once inside, the tiny microbe will travel to the rodents’ brains, forming cysts in a part of their brains associated with fear. Research shows that this causes reduced fear and anxiety in rats(Opens in a new tab), allowing cats to hunt and eat them more easily. And the cycle continues.
Parasitic mind control, folks, is real. But rest assured you won’t be chased by a Cordyceps infected zombie. At least, as far as anyone knows.