I've ripped a chicken breast off a whole uncooked chicken without claws... Same principle. Human fingers can tear flesh off bone if you use enough force and find the correct spot.
You brought up the answer in your own response. Broken Skin.
Tommy turned because he had a cut from a pipe bomb explosion. There was no indicated injuries or broken skin from
Riley and
Angel when they immersed themselves in the pile. Same can probably be said for clean up crews. So long as they don't have an open wound, you can touch the blood. You just probably shouldn't.
Am I saying there's no chance the virus/pathogen dies when outside the body? Not at all. That could very well be the case. And that could explain (getting back to the point of this thread) why the water doesn't get infected. All I'm saying is there is no real evidence saying the pathogen dies when it leaves the body
yet. We haven't seen it in action enough to rule out the possibility it's like bacteria that grows exponentially in the right conditions.