Unfortunately, it has been shown that alcohol hand sanitizers, like Purell, are not effective against norovirus. They kill other things, but not noro, and I guess it's better than nothing when hand washing is not available.
I was in Disney World a few months ago, and was turned off by the finger print scanners they now use to get into the park. I asked the attendant to clean off the scanner before I used it. Unlike elevator buttons, one can't use one's knuckle or elbow on a finger print machine!