Yep, it would be the smart thing to do. Then what about the next plane that arrives tomorrow with sick people on it, and the one in Chicago, and the one in Atlanta, and the one at Dulles, and the one at JFK... and on and on. Where are they going to start putting the thousands of potentially exposed passengers?
bump
If that many planes start flying in which are infected (your scenario) they will of course have to block off flights from those areas.