People talk about zombies as a matter of pure fiction, as an idea completely untethered to reality. These people don’t know that zombies already exist – just not yet in humans. But the biological mechanics are certainly already there. For another example, let me take a moment to introduce you to the fungus Cordyceps. In many insect species it takes over the brain of its host, altering the insect’s behavior before killing it and using the host to spread more fungus.
Don’t watch this video if you have a weak stomach (or do watch the video if you have a weak stomach, since you’re going to need to get over that shit fast if you want to survive).
One writer at Scientific American describes the killer fungus this way:
Not all of these parasites are the evil zombie-makers you might think. A few species of Cordyceps have medicinal value. One of these fungi, Cordyceps subsessilis, has been used to derive immunosuppressive drugs used in organ transplants. But some species of Cordyceps are indeed body snatchers—they have been making real zombies for millions of years.
And it doesn’t stop with ants and grasshoppers.
Other species of Cordyceps are just as transforming, even if they don’t turn the host into a faithful undead servant. Cordyceps ignota infects tarantulas. Its spores burrow into the spider, extending a legion of wispy fingers—collectively known as mycelium—throughout the body. The fingers are how the fungus grows, and how the spider dies. Once the tarantula’s insides are replaced with the fungus, fruiting bodies again burst forth to create art that could only come from such a bizarre demise.
Much like a disease relegated to a certain species can evolve to add new species to its list of potential victims (see swine flu/avian flu, etc.), it is not unthinkable that the Cordyceps fungus could one day add humans to its list of potential prey. After all, you heard the narrator in the video say that the greater the prey species’ population, the great chance they will fall victim to a Cordyceps infection. You’d have to look far and wide for a species that is more overpopulated than humans.
And when the fungus does make the cross-species leap, what can we expect? It’s possible that victims will merely become disoriented and harmlessly trip over things before dying. However, when humans become disoriented they tend to panic, and without the fullness of their reason present to check that fear it’s very likely the victims would become violent – even more so as their brains are eroded by the parasite.
Should this be how the inevitable zombie scenario manifests, what can you do? Not much, as it turns out. Anti-fungals take a long time to produce. The best thing you can do is to quarantine yourself for as long as possible and stay sanitary.