I have a theory
Fair warning. My english isn't perfect & this theory doesn't endorse my personal opinion or beliefs.
I've seen this movie a lot of times, throughout I might have figured out the background of this film and the reason of why the characters die.
I'm Christian and I think this movie is based on Christianity, morals. etc. but, I think the main reason of the "apocalypse" was taken too literal and far, as if sins were the worst thing you could do.
First of, the intro, the song. When the man comes around by Johnny Cash. If you read the lyrics it's about heaven, hell, the apocalypse. Something that a man with strong religious values would write, in this case Johnny Cash, the famous country singer that comes from a place in the United States where Christianity is strongly practiced.
Second, the reason of why characters die.
According for what I've learned about the bible and what the apocalypse book says. God stated that when the apocalypse comes, God will take to heaven all the people who's innocent. They all died from bite, and also bible says that somehow the presence of the first ones who die will torment the survivors in the end of the days.
Vivian, Louis - Both died when the disease started.
Nicole's father and the bloated woman - Both died a day after. (From all 4 we don't know that much but I could guess they have done nothing wrong with their lives).
Now, with the other characters.
*All of this characters died in a horrible way, according to bible, whoever survives and done wrong will suffer* (EXCEPT MICHAEL, HIS DEATH WAS QUICK, READ BELOW FOR EXPLANATION)
Bart - He was somehow bad and neutral, he always followed CJ, even if he wasn't that much of a bad guy, his legion was wrong. and he practiced sex out of wedlock.
Luda - She got pregnant and she wasn't even married. She was with a thief & possible murderer.
Andre - He was a thief, he did bad things, he probably killed someone.
Norma - She was a good lady, but she was a lesbian. We all could tell.
Andy - He was separated from his wife, about to get divorced, he was an alcoholic and loved violence. (see extras on youtube)
Tucker - I'm not sure about him, but judging by his looks he didn't have much education, and that could lead to him doing minimal bad things. Although he didn't suffer much, his death was quick. (Help me out in this one)
Monica - She was a whore, she was bisexual, she was probably a prostitute also.
Glen - He was nice too, but he was Gay and didn't believe in God.
Steve - He was a douche, he was a man full of lust, he was chaotic neutral, possible sex addict.
C.J. - You can tell he used to do bad things, he wasn't a happy man, probably killed people, selfish human being.
Michael - (This one's tough) I guess, he was a nice man, probably believed in God so his sins were minor, he was married 3 times, which means he was divorced 3 times and according to bible, God dislikes that blah blah. Maybe that's the reason why his death was quick and painless.
THOSE WHO SURVIVED AND EXPLANATION.
The end of the movie is to viewers decision, whether they survived or not. If you ask me, they did, cause they did nothing wrong. and the bible says, that those who did nothing wrong and survived will stay in earth as a reminder that God is restoring the world and his faith in the human after a plague. In this case (the zombie apocalypse).
Kenneth - He was a Cop, single, a good man, he believed in God, He did good things.
Ana - She was shown having sex, but she was married. doesn't matter. She was a nice woman, she helped others since she was a nurse.
Terry - He was young, he didn't do anything bad ever, he was a regular guy with strong morals, he didn't follow what CJ wanted him to do.
Nicole - She was young as well, she was a good girl, she didn't do anything wrong. possibly believed in God, she had good values from her parents.
(From Terry and Nicole, they were in love, and according to bible that's a sign that God didn't lost faith in the love that humanity could have.)
and Chips the dog - Nothing happened to animals since they're creatures protected by God and God dislikes when animals get harmed unless they're for human to survive eating them. (bible thing).
Final thoughts.
That's how i interpreted the movie, I don't know what you think about my analysis, it took me an hour to write it almost eloquently, so, please leave comments about what you think and if i missed something, please let me know!! Thanks for reading.