Trey Edward Shults uses his lens in a very specific way to create suspense and paranoia in the frame. First, we watch as Travis is seen sitting at the kitchen table between his parents as the camera pushes in on him while they all decide what to do with Will. The camera has an eery feel to it, and all we've seen of Travis to this point is that he has nightmares about the outbreak, we don't know if he is infected or just dreaming it, but the camera work makes us question it. We also see Shults craft a shot of Travis coming down the stairs with a lantern on the right of frame and the image is reflected in a mirror to the left of frame. This imagery creates the concept that Travis is in between two worlds and we don't know if his nightmares are taking over his reality.
Shults contributes heavily to the paranoia of the film as he is the screenwriter as well as the director. He purposefully sets the story in a remote location in the woods far outside of a major city in America. That's all we know. We also don't know what caused the outbreak, or how it is contracted. All of these factors heighten the tension in every scene as anyone new that is introduced has the potential to be infected, or to be dangerous (which we see with the two men who shoot at Paul and Will on the road).
Finally, Shults leaves the image of Andrew being sick completely out of the end of the film. We don't know if he is in fact infected or not because we never see him. This creates the reality of Paul and Sarah's decision to kill the family as they aren't sure what is happening before they pull the trigger. In situations like this, it is often the case that people don't have all the information they need to make a rational decision so, they instead find themselves at the mercy of fear.
