Dr. Irwin Redlener, the director of the Columbia University National Center for Disaster Preparedness, called the travel bans a “mixed bag" in terms of effectiveness.
Stopping travel from China was coupled with inconsistent messaging from the White House on the potential severity of the threat. On Jan. 30, Trump said the U.S. has "very little problem," and through February, Trump was comparing the coronavirus to a flu.
“There was value in closing the border to Chinese nationals coming to the U.S. in the early weeks of this situation. Closing the borders to Europeans later? It was too late to make much difference. It’s a mixed bag,”
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Nearly 40k flew to U.S. from China after Trump's coronavirus travel ban.
https://www.axios.com/coronavirus-trump-china-travel-ban-45a2da12-8063-4ad9-ba28-61cdeb1ce0b3.html