If the creepy, fungus-faced zombies of HBO’sThe Last of Us managed to keep you up at night, you’re not alone. With a plot that hits a little close to home after the SARS-CoV-2 outbreak of 2019, the television series centers around the survivors of a devastating fungal pandemic that has “mushroomed” far out of control.
The series puts the blame on a genus of fungi called Cordyceps, which is known for its real-life zombifying ability in insects. Should humanity be concerned about a mind-altering Cordyceps pandemic happening in the real world? Thankfully, the short answer is “no,” but before we discuss why that is, let’s take a closer look at fungi and the fascinating, frightening life cycle of a “zombie fungus.”
At first glance, fungi look a lot like plants in form and function, so it may come as no surprise that they were classified as part of the plant kingdom until the mid-20th century. However, thanks to advances in genetic sequencing, we now know that fungi actually share more characteristics with animals than they do with plants. Nevertheless, fungi are different enough from both animals and plants to warrant being the rulers of their own distinct kingdom today. Learn more about the unique features and ecology of the Fungi kingdom in this OpenStax pathway.
Fungi come in all sorts of shapes and sizes, ranging from tiny, unicellular yeasts to behemoths like the “Humongous Fungus,” as featured in this video from Animalogic. Most fungi reproduce via spores, which are microscopic reproductive cells that operate much like a plant’s seeds. Like animals, fungi are heterotrophs, which means that they cannot create their own food. Instead, they rely on outside sources for nutrients. Most fungi feed primarily on decaying organic matter, making them an incredibly important part of nature’s decomposition cycle.
Some fungi take a different approach to finding a food source, however. Fungi in genera like Cordyceps and Ophiocordyceps are parasitic, which means that a key part of their life cycle involves finding, infecting, and feeding on a host. It’s in this characteristic that The Last of Us found inspiration.
The infection begins when a spore comes into contact with a suitable host. The spore then penetrates the host’s exoskeleton and begins to settle into its tissues. Over time, the fungus feeds on the host, eventually replacing much of its victim’s body with fungal filaments—hyphae—and forms a network of tissue known as mycelium.
As shown in this video from Animalogic, the zombie-ant fungus (Ophiocordyceps unilateralis) has perfected this process. Once infected, an ant is compelled by the fungus to seek out a leaf or stem in a warm, humid area not far off the ground. The ant then clamps its jaws down on a secure part of the foliage, anchors itself in place, and dies. The fungus feeds on the ant’s insides until it’s able to produce a fruiting body, which extends from the dead ant and casts spores all around the area, starting the cycle again. A lovely image, right?
Now, back to the question at hand: could Cordyceps evolve to infect humans and create a real-life zombie pandemic? While the scenario is perfect for a television show, scientists say that such an event is incredibly unlikely. Fortunately for us, Cordyceps and its relatives have evolved over millions of years to infect specific host species (namely insects and other arthropods) and, as they currently exist, would not be able to survive the higher body temperature of a human. This means that the likelihood of the zombie-ant fungus going from infecting an ant to zombifying a human is slim to none.
In truth, fungi are more intertwined with our lives than we may realize. We bake bread with yeast, make anti-microbial medicine from mold, and keep our crops safe from pests using fungal insecticides. Even some species of Cordyceps, such as the caterpillar fungus (Ophiocordyceps sinensis), have had a place in traditional medicine for hundreds of years.
However, there’s no denying that fungal diseases do pose a significant and growing threat, especially due to climate change. As temperatures rise, it’s possible that fungi will adapt to the changing environment and put humans at a higher risk of infection. Scientists theorize that this could have already been the case with Candida auris, a fungus that emerged in 2009 and can cause serious infections in people who are immunocompromised. So, while Cordyceps may not be the zombie-making monster in real life that it is on screen, there are other fungi out there worth keeping an eye on!