Here’s How The Walking Dead‘s Zombie Virus Could Work

Yesterday, we welcomed The Walking Dead back into what's left of our lives. Wow, wasn't it crazy when [spoiler redacted]? No one saw that coming, huh? Well, now that the show is entering its fifth season, it's time we answered a very crucial question: What, exactly, is this zombie virus? Thankfully, in a new video for Nerdist Industries, Kyle Hill attempts to add a scientific explanation to the show's central, viral theme. We spoke with Hill for more of the logic behind the zombie apocalypse. Because science.

"Like all other zombie-themed media before it, The Walking Dead implies that getting bit by a zombie turns you into a zombie," Hill tells R29. But, the show's first season confirmed that this zombie-fication is due to a virus that we actually all have (but which doesn't affect us until we're dead). Here, things get a bit complicated. When something or someone carries a virus but doesn't necessarily suffer its effects, that person (or animal) is called a reservoir. For instance, we think that bats might be reservoirs for the headline-making Ebola virus. But, there aren't any instances of a virus that controls your brain. Parasites, on the other hand, can.

So, Hill suggests The Walking Dead zombie disease works more like a parasite, which can (creepily) control other creatures. For instance, the toxoplasma parasite can only reproduce in a cat's guts, so it lives in rats and mice and makes them attracted to the smell of cat pee rather than afraid of it. In this way, those rodents are much easier for cats to catch and eat — so the parasite can live on.

Caveat: The zombie virus doesn't control living victims. This leads Hill to suggest it's actually the bacteria in the biting zombies' mouths (and the subsequent victims' lack of access to medical care) that makes the zombie "disease" so deadly. In this scenario, the virus could actually be totally irrelevant; it could really be the bacteria that kills. But, it makes sense that survivors would just assume it's the virus that's deadly. This explanation is actually Hill's favorite, he says, "because it works out from a practical standpoint: These people don't have to be scientists; they just have to notice the pattern of getting bit and becoming a zombie."

We're always ready to dissect imaginary — but feasible? — diseases, and we look forward to learning more as the show continues. And, of course, we're excited to see more disgusting, scary zombies.