Originally Posted by Ghositex
The "NO HELP" sign was put there when they gave up trying to save bitten people, imo. Perhaps they couldn't give anyone else help, since we saw the Hospital was filled with walkers, and they didn't want more people asking for help. Or maybe, the Hospital just got overrun, somebody escaped, and just wanted to say there was no one but dead inside of the building.
This was my guess, too. I thought it was made somewhat early in the apocalypse, and was meant to say something along the lines of "if you are sick or injured, do not go to this hospital, you will not find help", because that's usually the place to go.