Plot hole: This could be a "suspension of disbelief" issue, but at the climax of the movie when the murderer's accomplice gets shot, Jack has to grab the rope to save the dangling Dean. Objects (including people) fall at 32 feet/second, and speed up after that. That's roughly 10 yards/second, which is the speed of a world class sprinter. Jack was a speedy fellow to get to that rope, especially with street shoes, no starting blocks, and a slippery surface to boot (not to mention his age).
Plot hole: In the scene where they go to the intern's apartment to find the key to go out the through the basement there is a moment where they can't remember which apartment belongs to the intern. When they ask the cop who did roll call he can't remember. Angela says that in order to figure it out they should go check the mailboxes in the lobby and match up the name. This would lead them back past all the infected people and undoubtedly make the movie more interesting but it would have been safer and quicker to rewind the tape in the video camera and see which apartment the intern claimed when his name was called.
Suggested correction: It definitely would not have been the safer option. Where would Pablo, Angela and Manu have stood while rewinding and starting the tape to get to the required footage? The apartments that are open all contain infectees (Ms Izquierdo, Jennifer, the young cop, Cesar, health Inspector), and the other infectees are roaming the hallways and staircases looking for survivors. It would have been far more dangerous to stand still out while rewinding footage, than to check the mailboxes.
Plot hole: Brewster gives Erica his gun to shoot the last perp, but it was HER gun that shot the other two. Brewster is going to have to convince investigating officers that the one perp killed the other two...or would they even care?
Plot hole: After the first death, Ian is in the office and after the conversation with the girl the scene starts to speed up, indicating that time is passing by at a fast pace; yet even with the rapid time change, the sun's rays that pass through the office never move or change in any way as it should.
Plot hole: Jim leaves to attend his family Christmas as evident by his dialogue in the opening scene, and evidently Carl is supposed to be at home to his family in the morning as well, but both are killed by Thomas. When the movie ends with Angela entering the city, it is early morning just before sunrise. Jim and Carl's families would have noted that they were not home on time, and therefore would have had someone searching for them. This makes it implausible that Angela's situation would not have been discovered.