This is only possible because China is a small island far from the initial outbreak of the pandemic.https://twitter.com/ArjunKharpal/status/1337967839320309760 …
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On the contrary, they have to be implemented quickly, or it's too late. Both Australia and NZ introduced travel bans very early.
I travelled from Milan, Italy to Australia (where I live) on February 24th via Zurich, at which point there was a travel advisory against China but no ban specifically. An outright ban was implemented mid-March. Not really that quick
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