Cesar: There's something more to this place. Our cells don't work. Neither does the T.V. Or radio. We're isolated.
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.