[Genuine Realist]

From the blog:

This chart shows the impact that the Wuhan travel ban had delaying the epidemic. The bubble sizes show the number of daily cases. The top line shows the cases if nothing is done. The two other lines show the impact if 40% and 90% of travel is eliminated. This is a model created by epidemiologists, because we can’t know for sure.
If you don’t see much difference, you’re right. It’s very hard to see any change in the development of the epidemic.
Researchers estimate that, all in all, the Wuhan travel ban only delayed the spread in China by 3–5 days.

A travel ban doesn't do much because once there is community transmission, local transmission increases exponentially.  The only way a travel ban is helpful is if it is so airtight that no new cases come in.  Otherwise, the travel ban (on its own) does nothing.  It's a little like the Chinese shutting the Wuhan seafood market (if that is how the animal to human transmission happened) after there was already human to human transmission.  Or, as they say, it's like closing the barn door after the horses have left.

Could a travel ban be useful?  If you can reduce local transmission to the point where the virus can be contained, then having a travel ban can prevent the reintroduction of disease from places where it is out of control, especially if you can't track and trace visitors easily.  But on their own, and in the setting of local transmission, a travel ban is like pissing in the ocean.  And worse, it distracts you from focusing on other things.

BC

I forget the category of human being who rushes in where angels fear to tread. But I will join that number by suggesting that the timing of a ravel ban is more important by quantum degrees than with other forms of social distancing. A restriction to a small geographical area must limit the spread of the virus. Surely, if the ban is imposed ASAP after the virus is identified, there is some reasonable chance to achieve that result.

What is not in dispute is that the travel ban on January 31st was too little, too late, and not effective at all.

[Genuine Realist]

From the blog:

This chart shows the impact that the Wuhan travel ban had delaying the epidemic. The bubble sizes show the number of daily cases. The top line shows the cases if nothing is done. The two other lines show the impact if 40% and 90% of travel is eliminated. This is a model created by epidemiologists, because we can’t know for sure.
If you don’t see much difference, you’re right. It’s very hard to see any change in the development of the epidemic.
Researchers estimate that, all in all, the Wuhan travel ban only delayed the spread in China by 3–5 days.

A travel ban doesn't do much because once there is community transmission, local transmission increases exponentially.  The only way a travel ban is helpful is if it is so airtight that no new cases come in.  Otherwise, the travel ban (on its own) does nothing.  It's a little like the Chinese shutting the Wuhan seafood market (if that is how the animal to human transmission happened) after there was already human to human transmission.  Or, as they say, it's like closing the barn door after the horses have left.

Could a travel ban be useful?  If you can reduce local transmission to the point where the virus can be contained, then having a travel ban can prevent the reintroduction of disease from places where it is out of control, especially if you can't track and trace visitors easily.  But on their own, and in the setting of local transmission, a travel ban is like pissing in the ocean.  And worse, it distracts you from focusing on other things.

BC

I forget the category of human being who rushes in where angels fear to tread. But I will join that number by suggesting that the timing of a ravel ban is more important by quantum degrees than with other forms of social distancing. A restriction to a small geographical area must limit the spread of the virus. Surely, if the ban is imposed ASAP after the virus is identified, there is some reasonable chance to achieve that result.

What is not in dispute is that the travel ban on January 31st was too little, too late, and not effective at all.