This movie kinda resembles a watered-down version of Pontypool, but also maybe the works on a similar concept to Stephen King's Cell because essentially, people trying to get help are making themselves vulnerable by unknowingly exposing themselves to the cause of the danger.
After she & her boyfriend break up, Sam witnesses people concerned with a guy with a nosebleed but thinks nothing of it and walks away. Later she meets up with her friends hoping to celebrate New Year's Eve. Unfortunately for them, when there's zombies running around that's not exactly easy.
Some group members try to figure out what's going on. It's a terrible idea though, because the social network they're communicating through is the cause of the infection. Which, unfortunately opens the movie to snark bait; at least some viewers, after finding out that social network regulars were becoming zombies, probably joked "finally, a genocide I can get behind!".
On the nosebleed guy - he's possibly the first attacker reported. Sam noticing him earlier is a relatable thing, because occasion, people have seen crimes being committed, didn't think anything of it, and only later release they were close to getting involved in the incident. I'd assume some members here have had something like happen.
The characters unfortunately aren't that developed. The ones who seem fun, easygoing types become cowards - at least one is doing the intelligent thing with his cowardice, but that might not be intentional on the writers' part - while quieter characters, those who become infected at least, act responsibly and attempt to distance themselves from the group before they turn.