[msandford]

There's an appeal to basic logic that goes "if the disease spreads from person to person and persons don't cross borders then the disease can't either." That might be a simplistic model but it's obviously correct upon inspection unless the disease spreads from distant persons which in this case it does not.

The reason you might reject the policy implications of said model is that the assumption going in (we can sufficiently restrict border movement) are in your mind impractical or impossible.