x-LucyLuu-x
I can't remember exactly where it was said, but the virus lays dormant in the body, and the body has to die first before it "activates." Considering everybody has been covered in walker blood at some point, has had scratches (not from walkers), and nothing has happened to them... I don't think blood or body parts entering their bodies would do anything.
But remember in season 2 on the farm when they wanted to get the zombie out of the well so it wouldn't poison the water supply and then in fell apart and they were like ooh can't use that well now.
The show is kind of really inconsistent about this matter.