Deliberate mistake: So right before the containment team seal up the window with the tarp, the SWAT is shown having police dogs. The virus (which came from a dog in the first place) can be transferred through saliva. The SWAT obviously overlooked the fact that the potentially infected people who might escape could be bitten by the dogs.
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.oddy knocky