Over the decades, the zombie film has become a cherished American institution. We love the moaning bastards so much that their rotting insides may as well be apple pie filling.
(Warning: Do not eat zombie insides, no matter how delicious. You will become a zombie.)
Like any institution, though, details may change but the core experience remains the same. When the zombie apocalypse comes, they might be fast or slow, the world could be post-apocalyptic or day-after-tomorrow, and the social commentary could be heavy-handed or non-existent, but the people you'll encounter will probably seem pretty familiar. Because if we've learned anything, it's that humans are only capable of six psychological reactions to a scourge of the undead. And here they are.
Every ragtag team of zombie survivalists will at some point have to deal with betrayal. No, I'm not talking about infidelity, although that too will likely occur (the zombie apocalypse is basically a free-for-all kinky sex-fest). I'm referring to the person who gets bitten by a zombie and neglects to report for immediate deheadification. Torn between fear of becoming a zombie and fear of getting shot in the face by their loved ones, they invariably hide their misfortune until they finally turn into a zombie and get shot in the face by their loved ones. Wouldn't it have been easier just to tell the truth?
Maybe she's a little quirky, but zombie? I just don't see it.
*Becomes pale, develops a corpse-like stink and/or requests to have "whichever rations taste most like brains."
*Turtlenecks, scarves or comically oversized watches are usually a bad sign.
*Claims to "really understand how zombies think. Like, really."
*Offers you admittance to the "Blood Brothers For Life No Shooting Each Other" club they just formed.
*You just saw them have sex with a zombie.
Chances of Survival:
Assuming you don't consider the shambling undead "survivors," nil. Unless the antidote/serum/Z-ray is discovered in the next 24 hours, they've basically bought it. The real question in the betrayer's case is how long they can last. If they're a beloved family member, they'll probably make it right up to the point where shooting them in the face will be most fraught with poignancy. If they're a mysterious drifter who just joined the team, they'll be biting bullet before the end of this reel.
Recommended Course of Action:
Argue heatedly with your companions about whether you really have it in you to kill a fellow human being, all while the human being in debate quietly passes out in the corner. Continue discussions until the infected person leaps at you with mindless hate in their eyes, then reflexively blow their head off. Never speak of them again.