China tried this in March and it failed rather spectacularly. Border officials were quickly overwhelmed and had to play it fast and loose; nobody knows who was responsible for what. In many cases, people showing symptoms who were supposed to be placed under medical observation were prematurely discharged, this plus some other oversight have resulted in at least one active disease cluster in Guangzhou. By the end of March the government had to massively reduce the number of arriving flights to make the passenger numbers more manageable.

As it always turns out, providing food and accomondation for tens of thousands of people is always easier said than done.