Some people have trouble going to movies. It's hard for them to suspend disbelief, especially when the director, script-writer and special effects get the science wrong. When I say wrong, I don't mean they have the nerve to suggest that time travel could work or people can fly. No, I'm talking about movies where the premise is embedded in reality but is still somehow unaware or in defiance of current scientific understanding. It's as if they expect the audience not to know any better. (Not only is that insulting, it ends up acting as a self-fulfilling prophecy.)
I have railed at movies that depict certain animals inaccurately (creating irrational fear outside the cinema!), and when characters with a mental illness do not act in keeping with what we know about the disease (in other words, the director relies on stereotypes of "otherness" for effect). The misunderstanding of basic biology, in particular, can make my skin crawl.
To my great relief, a movie I saw a few days ago didn't push my buttons - and it was a zombie movie, of all things! World War Z, directed by Marc Forster.
Of course, the movie expects a certain suspension of disbelief: for one thing, there is no such thing as the undead. (If an organism is still reactive and moving, it's alive. It may not have much quality of life, mind you, but it's not dead.) And the disease passed from the zombies via a ferocious bite transforms victims in mere seconds.
What I really liked about the movie--besides seeing a very intense Brad Pitt on the screen almost all the time, that is--is the zombie idea itself. The disease, which is never isolated and identified, affects a victim's brain. Suddenly, and I mean suddenly, the zombie becomes a twitchy, speedy, chomping machine with a single motivation: to attack human beings and bite them. That's all. There is no brain eating. The infected zombies want to recruit others.
The infection (which takes hold so rapidly) drives them to do this.
This is where the movie makes the most sense, scientifically.
In nature, there are many examples of pseudo-zombification, cases where a parasite - often a macroscopic one, like a fluke, but plenty of viruses, too - takes over the brain of the host and compels it to complete the parasite's life cycle. It's very, very creepy but true.
Example: toxoplasmosis, which makes rats lose their fear of cats, disinhibiting them to the point of actually asking Kitty to play. Kitty, not clear on the concept, eats rat, ingests parasite, excretes eggs at a later date.
Example: grasshoppers that commit suicide by jumping into pools, pleasing the parasites that have taken over their brains. (The worm needs water to reproduce.)
Maybe one day, some parasite will jump from another species and cause humans to act strangely around other people or maybe an intermediate host (which then infects humans). The parasite will change us to get what it wants.
It's horrible to contemplate. But it isn't all that far-fetched.