But it's an ER! There's a door open to the outside for ambulances! The ER is like the exact opposite of the OR when it comes to cleanliness!
You work at a hospital that requires scrubs to enter the ER? And has a problem with non-clinical people entering the ER, even though I would argue that that's the EXACT POINT of the ER?
Have you ever been in a real, modern emergency room? It's not one big charnel pit where they toss the swine flu patients in with the people with sucking chest wounds. Once you get past the waiting room--maybe what you're thinking of when you're talking about the "ER"--there are quite a few individual treatment areas. People with serious, immediately-life-threatening injuries and illnesses will bypass the waiting room completely, of course.
Plus, you seem to have no real concept of infection control. Just because there are X number of people with potentially contagious conditions doesn't mean that it makes any sense to make it X+1, and hospital personnel are as capable of being carriers as anyone else. If they really need to be in there, they can take the time to wash up and suit up and put on a mask.