When you enter a room and see a pile of dead bodies in a horror game, it's business as usual. In Dead Space, you can't tell if that corpse pile is just decoration or something far more sinister. The Infector enemy type just loves to ruin your day by re-animating the corpses strewn across the Ishimura and the Sprawl, something that can only be done if their corpse still has limbs. It's probably best you dismember the limbs of every corpse you see when you walk into a room then, just to be safe.