The word zombie conjures up images of the dead rising out the earth from their graves. It used to be the primary way people thought of the undead. Now, with pop culture and creative writers and directors, the zombie has evolved into a myriad of types and interpretations. There are types that are no longer undead, but people infected with a “rage virus” or people so removed from their own humanity that they go mad and become cannibals. Then there is the question of consciousness. Some types of zombie are mindless, others are able to think simply like we imagine cavemen to be like. They can even be intelligent and able to think as we do but with the desire to destroy and consume us driving them.
We know what zombies are, right? Now you’re probably wondering how likely it is for the dead to come back to life to feast on our flesh. Reality time, it’s not. Sorry, maybe science will blunder upon a way to re-animate necrosed tissue in some way but it won’t be the zombie apocalypse we’ve seen in the movies. I’m not an expert in biology but I know enough to apply some careful thought to this. What mechanism in nature exists that can re-animate dead flesh? I haven’t heard of one, maybe because it doesn’t make sense. Something that’s dead is food. Everything that lives in some way is trying to keep living.
So what does make sense? Well, the usual culprits are viruses, bacteria and parasites. There is a reason for this, there are real-world examples of each that (not on their own) could potentially lead to the apocalypse we fear.
Let us start with a virus like rabies. It can cause extreme aggression and altered behaviour but is often fatal past a certain point. In order for it to be a zombie virus, it would have to mutate in a way to not kill the person in the process. Cannibalism would be less likely and violence would be the main issue with infected people. The scary part of rabies would be the vectors of infection. Viruses can be transmitted through just about any medium including the air, making it one of the worse options.
Next would be bacteria. There are bacteria that can alter behaviour, notably toxoplasma gondii found often in cats and other animals. It can lower IQ, increase recklessness and alter attention span making the infected more susceptible to predators which benefits the bacteria. Infection vectors for bacteria and parasites are more classic compared to zombie lore. Infected bodily fluids and materials like blood, feces, and questionable water or food sources.
Time for the fun little guys known as parasites. There is a wide variety of parasitic creatures that can be as small as bacteria right up to insect size (like the Costa Rican and Jewel Wasp) with my favourite for creepiness going to the flatworm (or fluke). There are many (I’ll say too many) types of flatworms that hijack the brains of its victims making them suicidal and easy prey for predators.
One thing to help reduce that growing panic you be having is that any of these possibilities, even with mutation, are still highly unlikely to give rise to zombies on their own. Should any two or all three team up, then the human race will have a very unpleasant time. In nature, any of these organisms crossing paths will just kill each other. The possibility of just one unique host animal able to bridge the biological gap and create the (living) zombies we see in the media may be incredibly low but still possible.
No matter how unlikely zombies actually are, the official stance of the CDC is that if you’re prepared for a zombie apocalypse then you’re prepared for any disaster. Don’t believe me? Google it.
Stay healthy survivors.