Reasoning from purely a physical system perspective, I'm confident that a travel "ban" will slow its spread, especially the earlier you enforce it. But agreed

Reasoning from purely a physical system perspective, I'm confident that a travel "ban" will slow its spread, especially the earlier you enforce it. But agreed it will never be 100% effective. The question remains is the slowing worth the ban? Bans are painful, but any slowing will buy professionals more time to study it and begin targetted mitigations, and while the total infected is smaller than otherwise. Trade-offs...