Only a minority of countries are doing that. It might work now because most cases are in China. If self-sustaining outbreaks run out of control in Thailand and Singapore, will travellers from there be blocked too? It quickly becomes a game of cat and mouse.

This is unlikely. What is more likely is that all of Chinas poor neighboring countries are simply not reporting cases.

North Korea, Mongolia, Nepal, Northern Thailand, North Vietnam, North India, Eastern Russia, will keep this infection going until the next major outbreak next winter.