An article on how the keyboards at 2 University of Washington computer labs are super disgusting mentions that "At the [Seattle Public] library's Central Branch, all 378 public keyboards are wiped daily, cleaned thoroughly once a week and put through the dishwasher once a month on a rotating schedule."
At my library, no keyboard cleaning is done whatsoever. Now wash your hands.
CORRECTION! Apparently there is keyboard cleaning. Now lick your hands.