More on the notion of fighting Ebola by flight bans... I wrote about this, briefly, a few days ago. Nate Silver (a statistician by trade) makes essentially the same points I did, but in much greater detail.
A reader asked me (by email) why not simply change the criteria? Instead of banning flights from (say) Liberia, ban people from Liberia, as identified by their passports or visas.
That won't work, either, for very similar reasons. It would only work for Liberian citizens trying to travel to the U.S. It wouldn't work for naturalized Americans of Liberian descent (like, I believe, Thomas Duncan), as they'd have American passports. It wouldn't work for American tourists, students, or Peace Corps workers leaving the area. It wouldn't work for tourists from Europe who later travel to the U.S. I'd like to have concrete data on the percentage of people on airplanes arriving in London from Liberia who are Liberian citizens, but I don't. However, I do have some relevant experience: I have spent many, many hours in London's Heathrow airport and Frankfurt's airport, both of which are major hubs for airlines serving West Africa. I have watched hundreds of aircraft from Africa disembarking. I am certain that only a small percentage of those disembarking passengers were citizens of the departure country. How? It's very simple: they were overwhelmingly not black. They were Caucasian, Chinese, Japanese, Indian, or ... some other race, not black. A ban on people from Liberia would surely stop on a small percentage of potentially infected people from entering the U.S.
Underlying this notion of flight bans is the notion of a quarantine writ large. If we want to quarantine West Africa, the place to do it is in West Africa, not in U.S. airports. That would actually make sense, from the perspective of trying to control the epidemic. So far as I know, there is no precedent for quarantining an entire country. Liberia is a small country; its borders are only about 1,000 miles long. I'm sure a concerted, coordinated international effort to quarantine the country could be accomplished. Will it be? Not likely, unless things get much worse...