And where are you going to put 4,500 per month?
Seriously, I don't thinks that's a problem. I mentioned quarantine with a fee. Make it high enough to cover their expenses for three weeks as a guest of the US government. Or, they could just wait in a hotel room wherever they are until the 21 days is up. I assume most would choose the latter.
We wouldn't have to, once the word got out to the affected countries.
Lots of people would likely choose to wait it out in their home country, rather than stay in a quarantine facility in the U.S., where their chances of coming into contact with the infected would be much greater.