Epidemiologist David Dausey says, stop the flights now!
Individuals who suspect they have been exposed to Ebola and have the means to travel to the United States have every reason to get on a plane to the United States as soon as possible. There are no direct flights from the three most-affected nations, but passengers can transfer elsewhere, as Duncan did. If they stay in Africa, the probability that they will survive the illness if they have it is quite low. If they make it to the United States, they can expect to receive the best medical care the world can provide, and they will have a much higher probability of survival. So they are motivated to lie about their exposure status (wouldn’t you, in their shoes?) to airlines and public health officials and travel to the United States.
The fact there’s no direct flights makes it easier to lie. Hard to deny you were in Africa after stepping off a flight from Africa.