I was a bit taken aback by the suggestion that people from infected areas in Italy might travel to Switzerland because they believed they were not infected. That's how the virus has moved - people trying to escape infected areas and infecting people in other areas.
The incubation period is 2-5 days and up to 14 days for most people. Some people do not show symptoms for up to 20 days. Perhaps they're super healthy in the beginning. In any case, when people are in an infected area, it's foolish to transport them to uninfected areas - regardless of citizenship borders.
A male flew from Milan to NY yesterday and he said that he was questioned in Italy but was stunned that no one questioned him in the USA. He didn't appear sick but no one took his temp etc.
That IMO is a complete breakdown in the system (if there is a system).