I am just sitting here, reading everyone's take or predictions, and this is highly entertaining. I am loving this shit.
I wonder if what is so unbelievable, is that YOU are the Zombie/Infected. Everyone is trying to get away from you, and instead of you trying to build barricades to keep the zombies out, you are the zombie trying to get around barricades/etc to GET IN!
The ant fungi controls the ant, makes it go crazy and do things it doesn't really want to do, so maybe you are being controlled in a sense, and you are almost human enough to know what you are doing is wrong, but you can't stop.
I dont know, seems like all the decent Zombie/Infection style games have you as the hero trying to escape or survive. Well, Zombies have to survive too!