MacDara Conroy’s review published on Letterboxd :
Where to start with Mayhem? Let’s list the cons. It’s Yet Another Viral Outbreak Movie, for one. It’s Yet Another Workplace Satire, too. The cast of Serbs and antipodeans give up trying to hide their real accents as the plot’s literal clock runs out. The synth-driven faux-retro soundtrack is just like every other neo-exploitation flick you’ve seen in the last few years. ‘Derivative’ is the word that springs to mind.
But it works in spite of all of that. It’s smart enough to add a new twist to the zombie virus trope (there is a cure, it just takes a few hours to work) and it’s one that ups the stakes for what’s pretty much a let’s-play of a live-action ultraviolent sandbox game, played to a score courtesy of Steve Moore, who’s being doing this kind of thing with Zombi for years.
And those bad accents only add to its ludicrous charm, which is what really sets it apart from the likes of the similarly plotted but mean-spirited The Belko Experiment: it’s out to please the crowds, not ick them out. Does it go for the cheap pop? Sure it does. Did I still enjoy watching it? You betcha.