‘The Walking Dead’ Zombie Virus Makes More Sense As Venom

By Kyle Hill | February 17, 2014 12:27 pm
Photo by Gene Page/AMC

Photo by Gene Page/AMC

The virus in The Walking Dead makes no sense. As the show stands atop the corpses of many zombie entertainment pieces dead and gone, it seems to have taken on more than it can chew, per say.

Like every other zombie-themed frightfest, The Walking Dead adopts Rule #1 of the apocalypse: Don’t. Get. Bit. Why? Because every zombie mouth is filled with the virus that destroyed humanity. Even a scratch will put the pathogen in your blood stream, and unholy reanimation soon follows. This is the part that makes scientific sense. In the study of infectious diseases, epidemiologists would call zombies the virus’ reservoir. That is to say, there is a virus that resides within the zombies, causing them little to no damage, which can be passed to another host. For example, the reservoir of herpes B—a lesser known but much much more deadly herpesvirus—is found in macaques. It can mildly irritate the monkeys but kill nearly 70% of the humans it infects.

Most undead narratives end the rules here. Zombies have a virus that can be transmitted through blood and bites…stay away from these. But The Walking Dead goes further for the sake of an interesting story. And how far they go leaves only one scientific alternative—zombie venom.

At the beginning the second season of the show, we learn that everyone is infected already. All the characters on the show are carriers of the zombie virus, which presents itself upon death. If you die, you turn. If you get bit, you turn. If you think about it scientifically, it’s confusing. It goes back to reservoirs. When an animal is a reservoir for an infection, they don’t present the disease. The macaques that carry the deadly herpes B virus don’t die horribly from herpes B. Similarly, following what we know about viruses, a human that already carries the zombie virus would not die instantly from another injection of it. If everyone in The Walking Dead already carries the virus, getting bit would be just a bite.

You can’t infect the infected. But you could envenomate them.

Dead bodies are dirty. Shortly after our body stops fighting off bacteria and starts decomposing, we are colonized by microscopic critters not safe for the living. For example, the state of a corpse is dangerous enough that crews searching for victims of natural disasters take special precautions to make sure they don’t get infected. A rotting body can still transfer gastrointestinal pathogens, tuberculosis, and hepatitis [PDF] to the living. Tuberculosis itself can survive in a corpse for 36 days after host death. So, one can imagine that a biting mouth of a rotting corpse, continuously chomping down on humans, isn’t the most hygienic place. It harbors a cocktail of bacteria and viruses that could be considered a sort of “zombie venom.”

Keep in mind, “zombie venom” is my general term for specific bacteria or viruses in the mouth of a mindless attacker that gets injected into you and messes you up. Actual venom is more complex than that. The venom that oozes from the glands of some snakes, for example, is made of proteins, and is the result of a million years of complicated and fascinating evolution. Even so, the result is the same. When a zombie chomps down on you in The Walking Dead, it’s a death sentence. Because a reservoir for a virus doesn’t die from the virus it already carries, what kills a Walking Dead character must be this “venom” made up of bacteria and other viruses associated with decomposing corpses. Without any antibiotics, access to working hospitals, or medical training, the bite is effectively venomous. We have to label it this way because although bacteria and viruses are literally everywhere, only the organisms that live in the saliva in zombies seem to kill. When Rick has a non-zombie inflicted open wound, he survives.

Scientifically, I’m making a few jumps in logic here. But infection and viral transmission are health problems we understand the basics of, and their interpretations in The Walking Dead are simply at odds with what we know. For example, if the zombies were the reservoir for a virus that also kills people—as the show implies—pretty much any contact with any surface even near a zombie would be deadly. It would practically be the Middle Ages—scraping your wrist on some sharp outcropping would be the last thing you ever do.

Adding insult to zombie injury, complicating the aspects of infection hardly adds any value to the Walking Dead narrative. The death-to-reanimation scenario was used a few times in the show to little effect, and though it was a major reveal in the second season, it didn’t really change anything. There are already zombies everywhere, adding more with any kind of fatality is just more of the same.

One of the few times the show’s backwards notion of viral infection actually worked was when a deadly influenza-type virus swept through the group of survivors, killing and therefore zombifying many. But in those few episodes, the scariest part was who was going to get infected. It was the reality of being powerless to fight an invisible foe that added to the narrative, not the made-up rules of becoming undead.

When The Walking Dead decided to mutate the virus trope of modern zombie stories, I think they created more confusion than clarity. Questioning fans are right to find it odd when a virus supposedly kills a human that already carries that same virus. Like it or not, science fiction typically needs to bend but not break the laws of science to contribute to the genre. A sort of zombie “venom” made of bacteria and viruses unrelated to the outbreak would do just that. Maybe the show was strapped for scientific concepts and had to inject every plot point into the same vein. Maybe scientific accuracy was sacrificed for “better” storytelling (which sometimes is OK). But if you want to make the zombie apocalypse feel real, complete with CDC analyses and homespun rules of viral transmission, you can’t circumvent virology itself.

Part of this post was adapted from an earlier post linking zombie mouths—incorrectly—to komodo dragons. I have taken out that part, as komodo dragons do not kill with dirty mouths, but actual venom!

If you want to read a great book filled with stories and the science behind human infectious disease, check out David Quammen’s Spillover.

CATEGORIZED UNDER: Health & Medicine, top posts
  • http://www.americablog.com/ Naja pallida

    Walking Dead takes much of its zombie lore almost directly from Romero, and the Living Dead movies never really explicitly state what caused the zombie outbreak. Though there was plenty of speculation from the characters; a virus, mutagenic chemicals, something from space, radiation, failed attempt at biological warfare, etc. In The Walking Dead the number of times people are completely splattered with zombie gore, including in their mouths, eyes, open wounds, probably discounts any kind of bodily fluid transfer as the primary cause of transforming. The concept that it seemed to happen everywhere, all at once, also discounts simple person-to-person transmission.

    • Kyle Hill

      That’s a really good point. But for as much as the evidence in the show suggests, the narrative constantly drives home the point that a virus is at work here. In the CDC, the way they deal with infection (i.e., cutting off limbs), it all suggests viral transmission, which is of course the problem. When the virus is coupled with the other contradictory aspects of the show, it all starts to break down, making it hard to analyze with any science.

  • B Man

    Actually in walking dead everyone already has the virus that turns you into a zombie in their bodies. If you die from old age you’ll still become a zombie. It’s the zombie bite that causes you to come down with a deadly fever which kills you, much like the bite of a komodo dragon would in real life.

  • Lacey Arroyo

    Think about this for a moment…since they are already infected maybe being bit by a zombie isn’t what kills them but the bacteria that you yourself described that is in the deads mouth. It would be like having AIDS and then catching a cold and dying, the AIDS didn’t kill you just made you more succeptable with a weaker immune system….hole in your theory

  • Roy Hensley

    it actually makes sense to me. while you are alive you are able to actively fight off the virus and keep it at bay. but if you are killed then your immune system shuts down.. during this time the virus acts and reanimates the cells of the body thus bringing you back to life with no immune system. A bite from a zombie simply leads to sepsis and then death followed by re-animation.

  • Michael Brady

    Interesting. Your theory speaks to why zombie blood, brains, or other bodily fluids are not infectious. You can apparently smash, splash, and splatter walker skulls all day long without any fear of getting goo in your eyes, mouth, or breaks in the skin. Biter spit is the only real deal. Problem solved.

  • Em

    I’m sorry to nitpick but it’s PER SE, not PER SAY. Please understand the terms you are using and maybe don’t use expressions you don’t understand the meaning of – until you’ve looked them up. In fact the term ‘per se’ doesn’t even fit the context of your opening paragraph. It’s like you’ve just added it on the end of a sentence for no reason. It’s serving no good purpose there.

    Also, I’ve just noticed on a re-read – the expression is ‘bitten off more than it can chew’ not ‘taken on more than it can chew’.

    Interesting theory. re venom vs. infection though. The science of zombies in the show doesn’t make a lot of sense.

    • jam8838

      Everyone is a grammarian. Or is it, “A grammarian is everyone”? Sheesh. Talk about adding something for no reason–in this case, a comment on expression and grammar, without nothing to add to the discussion. I’m not being a troll, but, as someone with a MA in English (which is hardly something to brag about), I really dislike when people try to give English lessons online.

  • Daniel Rivas

    The venom theory holds if you remember that the surviving scientist in the CDC was not the best scientist there. He was only the most alive. He was able to learn some stuff about the virus but not everything. A zombie bite full of bacteria, viruses , fungi, and possibly prions. That could be what kills a person, then the virus is what reanimates them.

    All I’m saying is that a lonely, drunk, scientists who just lost his wife is going to have trouble making the most important breakthrough in medical history. His wife is probably the one who got him the job.

  • EMacAonghusa

    Have to agree with Ron there. Makes sense.

    A person can carry HIV for years and never develop AIDS for example. They are only said to have AIDS when when the numbers of specific types of cells in their immune system drop below a certain level. Maybe zomibe saliva overloads their immune system causing them to turn right away or maybe the virus mutates after death into a more potent form than that being carried by the living.

  • TheBrett

    I think the idea of “everyone is bitten” makes it more clear that there’s no real “escape” from zombies. Even if they settle into communities and wipe out all the extant zombies (or they all rot away over time), they’re always going to have to take preparations in case someone dies in their sleep and turns, or gets sick and dies (and turns), and so forth.

    It also makes the Fall a little more believable, although not by much. That’s probably why Romero was smart enough to end his first film with a bunch of local police and farmers forming a line and shooting all the zombies with hunting rifles.

  • http://sterlinganderson.net Sterling Anderson

    I don’t think you’ve done your research. The reason they try amputation when someone is bit (Herschel) is because they know everyone is infected and make an educated guess that it is infection that kills when bitten. They are making no assumption that bite == death from virus.

  • http://www.openbuddha.com/ Al Billings

    This article is flawed because both comic and show make it clear that simply dying turns you into a zombie, cause unknown. The bite is only bad because it is so full of pathogens that you get infected and die.

  • Boomer0127

    I think you may have missed the best part of the comparison. BV is a herpesvirus, yes, but all herpesviruses establish lifelong latent infections in their (natural) hosts. Yes BV is mostly an acute problems in humans, but if this was a different zoonotic herpesvirus perhaps it would be unable to cause acute disease but could still establish LATENCY. Latent herpesviruses are stimulated to reactivate, and in this case the herpesvirus reactivates causing the host to become “undead”. The stimulus would be either something in the bite of the walker OR the general stimulation of death itself – including one commenter’s idea of a lack of immunity holding it at bay. This could also explain the random amount of time it seems to take for the dead to reanimate as the undead – variations of the copy number of the zombie herpesvirus genome in the latently infected brain or possibly the ability for some people to repress the genome better than others. The possibilities are endless! Maybe science could even make a cure to remove the zombie herpesvirus genomes with targeted nucleases like ZFNs.

    Oh, and I disagree with your title – but yes simplex! In this case, herpes is forever and ever.

  • superninja

    The actual explanation given by the author of the comic is exactly what is proposed in the article, that it’s not a virus that kills you, its the bacteria in the zombies mouth. So yes, that would make more sense than the virus killing them, which is why that’s exactly what happens. Don’t get me wrong, it’s an interesting article, but it’s just pointing out something that’s already been accepted and acting like the creator didn’t already come up with it.

  • Hypothesis

    Interesting to read, but I agree with some of the other comments– there seems to be a lack of understanding of the very material this article is covering. It’s thought provoking, but overall seems to be trying to poke holes that aren’t there. For instance, and I think some of this was mentioned, there’s the possibility of latency.

    But let’s just walk through everything.

    First of all, if memory serves, there’s actually no clarification as to whether this is a virus or a bacteria, or even a fungus. To be honest, that was the most bothersome thing to me, scientifically speaking. You should be able to look at a normal cell, and an infected cell, and tell what the difference is. Of course, if people only started studying after everyone was, unbeknownst to them, infected, then it would be hard to get a clean sample and an infected sample from the same person, but still, there should be an obvious difference between ‘normal’ and ‘infected’ and they should be able to at least somewhat identify what it is.

    But ignoring that, the fact is that everyone’s infected with…. whatever this is.

    Which, given they aren’t all dying and showing symptoms, suggests its a virus, but most likely a retroactive one, which embeds its DNA into its host, to be replicated along with host DNA, proliferating throughout the body, but without activation. That is, until something does activate it. Such as, perhaps, some active enzymes in the silva of a zombie, as a bite would do. Or, perhaps, the chemical process the body undergoes during death, which would explain the alternative process of ‘zombification’.

    In the case of a bite, the body is ambushed with an active version of the virus, which could then create a chemical process to activate all the latent pieces of DNA in the hosts cells, creating more of the virus, and ultimately destroying the host. Basically, its like a bunch of soldiers running in and waking up the forces that had already infiltrated the base.

    In the case of death by other causes, the process is essentially the same, but its more chemical. To use the above analogy, its basically like the soldiers that infiltrated waiting for the base to empty out, before leaping to action and taking over.

    Then there’s the fact that this could be something else /entirely/. If you think about what a virus is– a bunch of DNA or RNA surrounded by a capsule of proteins– its a bit mind boggling. To think something like that developed, and evolved, and /thrived/, when it really doesn’t do anything except toss its genetic material into a cell and commandeer that cell to make more of it, means there’s a very strong possibility of something else, something completely different and unexpected, popping up, or already existing, and doing the very same thing. After all, we still don’t know about everything on this planet. For all we know, the ‘zombie virus’ could be neither virus, nor bacteria, nor fungi, or any other known infectious agent. It could be something new entirely.

  • Justin Tucker

    I think a bite from a walking corpse would carry all kinds of other bacteria and viruses that would cause the rapid fever onset leading to death then the ‘zombie’ virus would reanimate the newly deceased.

  • http://ethlenn.blogspot.com/ Ethlenn

    I think the zombie bite just speeds things up. It’s like the HIV case, a person can live for some time with it as long as one doesn’t get a bad immunology system targeted disease (ie. like heavy flu).
    For me it makes sense, a whole humanity may be infected but it’s a “sleeping” form which gets activated in certain circumstances. Bite just acts as catalyser in all this.

  • Bigmac4665

    When you get bit in the walking dead it was the fever that is deadly. Also why do the zombies only decompose to a certain point, the virus must have some way of protecting the vital musculoskeletal system. Also you have to think why the zombies are hungry. If the purpose of biting is to spread the disease then why do they actually consume the flesh? In my opinion the iris seems to have some way of substituting its normal fuel (digesting the remaining musculoskeletal system) for the renewable flesh of humans and animals. For instance when the doctor was studying michonnes armless jawless walkers he said they were starving, just very very slowly. Food for thought

  • Kevin Kelly

    Wow, worst.article.ever. The Walking Dead isn’t even ABOUT the zombies. It’s about the people. So who cares how the zombies work? Stop dissecting the show and start WATCHING it. Also, it’s per se, not ‘per say’. It’s a latin phrase that means ‘by itself’.


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About Kyle Hill

Kyle Hill is a science writer and communicator who specializes in finding the secret science in your favorite fandom. His work has appeared in Wired, The Boston Globe, Scientific American, Popular Science, Slate, and more. He is a TV correspondent for Al Jazeera America's science and technology show TechKnow and a columnist for Skeptical Inquirer magazine. Find his stream of nerdery on Twitter: @Sci_Phile Email him at sciencebasedlife [at] gmail [dot] com.


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