Putting the Science in Zombie Apocalypse

Kristi is an aspiring sci-fi and fantasy writer from Vancouver who also happens to be a scientist. She has a Ph.D. in Zoology from the University of British Columbia and a M.Sc. and B.Sc. in Molecular Biology and Biochemistry from Simon Fraser University. Her areas of expertise are cell biology, genetics and molecular biology.  Besides being an avid sci-fi fan, she is passionate about science literacy and introducing people to science through entertainment and fiction.  She is also a blogger for the Society for Canadian Women in Science and Technology (SCWIST). 

Putting the science in zombie apocalypse
The monsters in popular sci-fi and fantasy change at a rapid fire pace. While vampires and werewolves traditionally duke it out for the number one spot, recently the zombie has charged (mindlessly) into the schoolyard scuffle to seriously take on the top two contenders.

Let’s just say for a mindless horde it’s been a pretty spectacular effort.  Forget the schoolyard name-calling and fist fights, zombies showed up to the schoolyard ready to take on the cool kids with baseball bats and rebar.

Though zombies have always been a mainstay of modern sci-fi and fantasy, they’ve recently exploded on the fiction universe with appearances in reworked classics (Pride and Prejudice and Zombies), new novels (The new Guillermo Del Torres series, World War Z, My Life as a White Trash Zombie) video games (Left for Dead, Dead Island, Dead Space, Resident Evil), too many movies to count, and a spectacular debut into the prime time TV arena (Walking Dead anyone?).

But their recent popularity begs the question, why hasn’t the science of zombie’s caught up? As a scientist, I often get asked whether the viral zombie model would actually work and it’s a hard question to answer.  What it comes down to is that the virus model is outdated. We now know a hell of a lot more about the ways cells, viruses, genes, and diseases work.  When the whole viral zombie disease notion became popular, it was a great premise with the knowledge available at the time.  That’s a pretty big caveat, but it goes further than that.  It depends what you’re definition of a zombie is. The old Haitian/voodoo zombie has come a long way, from simple possession to a walking, rotting, infectious corpse, and the evolution doesn’t stop there.  Space zombie’s anyone?

All that stuff to think about, it’s no wonder authors shy away from the science side; and let’s face it, the scientists don’t make it easy- communication isn’t one of our strong suits. So how do we design a better sci-fi zombie? Something that gets our zombie out of this virus rut and into an identity that reflects the scientific leaps and bounds over the past 30 years? More than that though, how does an author out there approach the science design questions and reconcile it with their story?  Reading up on the history of infectious diseases and taking a first year course in cell biology seems a bit harsh and extreme for a potential two lines in a book.

Using the common zombie as a model what I want to do is show authors out there how they can work through the mechanistics of a scientific problem and apply it to any scientific question they come up against in their writing.  I think what will surprise most of you is how large of a role common sense plays.

So let’s begin. Imagine that we are presented with an eminent zombie infestation. We need to figure out how the zombie infection spreads and what we’re dealing with using the scientific method: observation and posing more questions.

1.  Memoirs of an Infection

Being a smart zombie-apocalypse savvy individual at the first sign of infection you hunkered down in a stronghold stadium with a handful of trigger happy friends and the majority of the Wal-Mart firearms section. Refugees bang on the locked and heavily barricaded doors of your stronghold, a horde of zombies hot on their trail. If you plan on letting them in you need to figure who has and doesn’t have the disease. Using the news feeds covering the disaster around the globe, you quickly realize only humans get the disease and you have to be bit. Scratches and bodily fluid splatter don’t cover it.  As you watch a newly zombified news reporter dive for his screaming anchorwoman, bit by a cameraman not five minutes before, it’s obvious that once bitten you’re time is numbered -no chance for rerolls here. A quick scan of the activity outside you’re stadium shows refugees climbing the fences and trying to fight the zombies off. Someone’s dog abandons the refugees and the zombies take no notice. The only thing stopping them is damage to the head, until then they’re biting every inch of the way.  You gulp as the first zombie grabs the chain link fence and climbs up after the screaming refugees. So much for the stupid zombie myth.

Now, without a tissue sample or time (you need to start shooting the zombies and/or refugees- I’ll let you decide what kind of a zombie survivalist you want to be) what can we deduce from our observations? Preferably in time to let some refugees in?

1. The infection is in the saliva. Only bites pass on the infection so chances are very good it’s carried in the saliva.  Even if the disease agent has orchestrated an entirely different infectious secretion (ie residual teeth or tentacles), we know it’s in the mouth. Avoid the mouth and you should be OK.  Another thought to keep in the back of your head is that the mouth is a great target to prevent spread- take out the mouth and even if the zombie is moving it can’t infect you!

2. Damn, it’s efficient. In almost every case of mainstream zombie-ism, the disease agent is one hundred percent effective.  One bite equals one disease. This is an important piece of information because it means that the agent completely bypasses our defense mechanism, the immune system. This is rare. Our immune systems can mount an attack on almost anything that can infect us.  Some diseases are better at evading it then others, but there is always a chance our immune systems will recognize and destroy the intruder in time.  That the zombie agent has a perfect record suggests it’s either incredibly sophisticated, OR it takes a sledgehammer approach.

3.Needs to eat human brains/living tissue. I think this is pretty well a unanimous expectation of zombies everywhere; they need to chase you down and try to eat you.  The reasons are usually foggy and what they are after is pretty foggy. But rest assured, you will need to run because they want to eat you.  But why the eating? No respectable infectious agent gets the host to do something for no reason.  At its most basic, the zombie needs to chase you down to pass on the infection.  But that can’t be it- stopping to eat cuts down on chasing and infection time. What the eating tells us is that the infectious agent doesn’t want to burn out it’s host out like a virus will- it’s got a vested interest in keeping it’s host alive.  The eating allows the host to refuel and keep a skeleton crew of neurons alive so the zombie can keep on chasing and chomping.

4. A hijacked nervous system.  Speaking of neurons, this infection has hijacked the entire nervous system. From a disease perspective this is really great evolution at work (there is also precedence for it in the real world). What good infectious agent wouldn’t want access to its own personal meatbag nervous system? Not only does its host carry it around from place to place, but when the infectious agent itself is hungry or otherwise in need of attention, it’s got something better than an optic fiber cable hard wired in!  Good-bye self-control, hello need for brains!

5. What is the infectious agent?: We now have a good idea what makes this disease tick so what is it? Without a tissue sample it’s impossible to tell for certain, but we CAN deduce the nature of the infection. So what are we likely dealing with? Virus or parasite*? All the observations we’ve made so far make a case for a parasite, not a virus.  Though it’s not a hard and fast rule, viruses infect to reproduce, whereas parasites infect to get a home, freeload, and live out their lives.  This is because their respective goals, or ‘business models’ are different. Although parasites and viruses both need to infect a host and use its resources’ to survive and reproduce, their global outlook is very different. A virus’s business model is based around hijacking your cellular machinery and completely depleting any and all resources it can get its grubby hands on. This goes on until the host dies or the immune system kicks the infecting virus out (OR into hibernation. Fun fact: a lot of viral infections are permanent, our immune system just gets used to them and forces them into retirement or hibernation Ex: Chicken pox, herpes, warts, and hepatitis). Success to a virus is making a gazillion infectious copies of itself whatever the cost.  Absolutely nowhere in this business model is there any accountability or design to save the host; it banks on having an inexhaustible supply of hosts available to infect in the future.

Parasites use the host as environments rather than strip mines.  A parasite needs to inhabit and use its host as a resource but it also needs the host to survive long enough to complete the parasites own life cycle (grow, reproduce etc). That doesn’t mean parasites show a lot of altruism towards their hosts but killing a host before completing the lifecycle is an automatic fail.  (After its life cycle is over it can kill the host all it wants, but not before).

So what does this mean for our zombie infestation now scaling the stadium fence outside our barricaded walls? Knowledge and a still functioning internet are powerful tools! We have a better idea what we’re dealing with and can start figuring out how to fight this parasite on a cellular level!  Now, time to call the CDC hotline and run a Google search for how to best collect tissue samples …right after we shoot some zombies…


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  • Holy CRAP! I had no idea!!! Thanks Kristi! Now I’z got the skills to pay the bills. C’mon you zombies…bring it.

  • Loved this post! Parasites really are the best contender for zombie miro-organism–can’t help but think about those parasites that turn ants into little ant zombies … shudders.

    • Kristi Charish

      Thanks Wendy! Don’t forget the brain parasite carried by cats that makes us more sympathetic (not in North America though!!)

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  • Marie Gilbert

    Really enjoyed reading this post. My zombies are alive, but after eating food that has been tampered with using bio-warfare over a long period of time, they become uncontrolled eating machines. When the person dies, the parasite seeks a new body.

  • Wow.Remove the insect cycle part of Plasmodium Falciparum life cycle and you have a great agent for causing Zombie apocalypse.Thanks for the great article.