I don't see how this is remotely economically enforceable.
We don't live in hermetically sealed bubbles, and can't. Normal hygiene should protect most people. If someone is showing signs of ebola, then there should be enough warning to deny the person boarding. Anything less serious then that, and most urban dwellers are already exposed to far more germs each day in the city (Buses, subways, public doors, tables, etc., ) than they are on a plane. And will likely be exposed to more germs at WDW than on the way there, too.
I'm amused that the more "green" and "back to the earth" we're urged to become, the more anxious of earth's germs we are.
Dirk