[simonh]

When you have an initial outbreak, you have a single original source of the incident and no possibility of people outside the area bringing in additional sources of the virus, because the virus hasn't spread outside the area yet. If you contain it locally, you have contained it completely, full stop.

The situation for other countries is completely different. Someone could fly into Japan right now from anywhere in the world carrying the contagion at any time. It was brought into Japan by multiple carriers at different times and different places. You can contain one incoming source, and three more will spring up. It's a completely different problem.

[bluGill]

No you don't, there is 27 days incubation factor which means 27 days before the initial outbreak for things to spread and no possible way to do anything about that. Then you have whatever time for doctors to identify that this is something new and a big deal, again time that things can spread without your ability to control it.

[lbeltrame]

The 27 days incubation is the maximum observed time. The median time is about 8 days.