So you've got a planeload of people coming into Dulles from Frankfurt. One of the passengers has an originating passport stamp from Liberia. What do you do with the 300 people? Do you quarantine only the passenger from Liberia, or do you quarantine everyone because they were in close promiximity to someone who is coming from an "ebola country" (even though it is highly unlikely that he himself was infected). How long do you quarantine for? Where? And if you send them back, won't you simply risk infecting even more people with ebola?
And what about the other ten planes that have landed since the Frankfurt flight, all with one or two people coming from West Africa?