Chances this could cause a zombie apocalypse:

If the whole sudden, mindless violence idea seems far-fetched, remember that you are just one brain chemical (serotonin) away from turning into a mindless killing¹ machine (they've tested it by putting rats in Deathmatch-style cages and watching them turn on each other). All it would take is a disease that destroys the brain's ability to absorb that one chemical and suddenly it's a real-world 28 Days Later.

So, imagine such an evolved disease, which we'll call Super Mad Cow (or, Madder Cow) getting a foothold through the food supply. Say this disease spreads through blood-on-blood contact, or saliva-on-blood contact. Now you have a Rage-type virus that can be transmitted with a bite.

Just like the movie. With one bite, you're suddenly the worst kind of zombie:

A fast zombie.

Neurogenesis

As seen in ...

Laboratories around the world.

What is it?

You know all that conversy out there about stem cell research? Well, the whole thing with stem cells is that they can basically be used to re-generate dead cells. Particularly of interest to zombologists like ourselves is neurogenesis, the method by which they can re-grow dead brain tissue.

You can see where this is going.

How it can result in zombies:

You wanted the undead to make an appearance in this article? Well, here you go, you creepy bastards³.

Science can pretty much save you from anything but brain death; they can swap⁴ out organs but when the brain turns to mush, you're gone. Right?

Well, not for long. They're already able to re-grow the brains of comatose⁵ head trauma⁶ patients until they wake up and walk around again.

Couple that with the new ability to keep a dead body in a state of suspended animation⁷ so that it can be brought back to life later, and soon we'll be able to bring back the dead, as long as we get to them quickly enough.

That sounds great, right? Well, this lab dedicated⁸ to "reanimation research" (yes, that's what they call it) explains how the process of "reanimating" a person creates a problem. It causes the brain to die off from the outside in. The outside being the cortex, the nice part of you that makes humans human. That just leaves the part that controls basic motor function and primitive⁹ instincts behind.

Reanimation research (artist's rendering)

You don't need the cortex to survive; all you need is the stem and you'll still be able to mindlessly walk and eat and enjoy Grey's Anatomy¹⁰. This is how chickens can keep walking around after they've been beheaded (including one case where the chicken lived for 18 months without a head).

So, you take a brain dead patient, use these techniques to re-grow the brain stem, and you now have a mindless body shambling around, no thoughts and no personality, nothing but a cloud of base instincts and impulses.

That, ladies and gentlemen, is what we like to call a real, live, undead fucking zombie. So there.

Chances this could cause a zombie apocalypse:

Think about it. Under every legal system in the world, all rights and responsibilities are terminated at death. All it takes is someone with resources and a need for a mindless workforce¹¹ of totally obedient slave labor².

How long until somebody tries this? We're betting somebody in the world, maybe North Korea, will have a working zombie by Christmas.

Nanobots

As seen in...

Michael Crichton's novel Prey¹², The PS2 game Nano Breaker

What are they?

Nanobots are a technology that science apparently¹³ engineered to make you terrified of the future. We're talking about microscopic¹⁴, self-replicating robots that can invisbily build--or destroy--anything. Vast sums of money are being poured into nanotechnology. Sure, at some level scientists know nanobots will destroy mankind. They just can't resist seeing how it happens.

How it can result in zombies:

Scientists have already created a nano-cyborg, by fusing a tiny silicone chip to a virus. The first thing they found out is these cyborgs can still operate for up to a month after the death of the host. Notice how nano scientists went right for zombification, even at this early stage. They know where the horror is.

According to studies, within a decade they'll have nanobots that can crawl inside your brain and set up neural¹⁵ connections to replace damaged ones. That's right; the nanobots will be able to rewire your thoughts. What could possibly go wrong?

Chances this could cause a zombie apocalypse:

Do the math, people.

Some day there will be nanobots in your brain. Those nanobots will be programmed to keep functioning after you die. They can form their own neural pathways, meaning they can use your brain to keep operating your limbs after you've deceased and, presumably, right up until you rot to pieces in mid-stride.

The nanobots will be programmed to self-replicate, and the death of the host will mean the end of the nanobots. To preserve themselves, they'd need to transfer to a new host. Therefore, the last act of the nanobot zombie would be to bite a hole in a healthy victim, letting the nanobots steam in and set up camp in the new host. Once in, they can shut down the part of the brain that resists (the cortex) and leave the brain stem intact. They will have added a new member to the unholy army of the undead.

Now, it should be more than clear by this point that our goal is to be responsible researchers. We don't want to create a panic here. All we're saying is that on an actual day on the actual calendar in the future, runaway¹⁶ microscopic nanobots will end civilization by flooding the planet with the cannabalistic undead.