That would be my assumption as well. I would hypothesize that once the virus is well seeded within a country, the contribution by new travelers is dwarfed by in

That would be my assumption as well. I would hypothesize that once the virus is well seeded within a country, the contribution by new travelers is dwarfed by internal propagation. Using the famous Washington Post simulation as a reference: https://www.washingtonpost.com/graphics/2020/world/corona-simulator/ https://www.washingtonpost.com/graphics/2020/world/corona-si... I imagine it's like the second scenario in reverse. Rather than the wall opening, picture it closing after the virus is already spreading uncontained on either side. Of course, it could be a significant factor in keeping the outbreak initially contained. But that involves an even more fanciful assumption in my view: that you could impose and really tightly enforce a ban early enough to matter. The continued pressure from Trump and many of his political allies to "open the economy" -- and their resistance to "shutting it down" in the first place -- shows such a proposition, offered at a point it would have mattered (if that were even possible with the initial stonewalling by China on the severity of the outbreak) would almost certainly have been cried down as paranoia and overreaction by the kind of business and political interests who hold real influence over these matters.