I was listening to a Virus Researcher here in the U.S. on CNN late tonight

What he said was this virus is so different than the one we have now in the way it attacks cells that it makes it much more likely to cause fatalities and 70% more contagious than the one we have now here. 

And when you hear that 60% of the new cases in London are the new more contagious and lethal one it is pretty likely that the newer more contagious and more lethal one is also almost everywhere on earth already that passenger planes travel to.

So, even closing borders to UK I would say It likely is too late for not only the U.S. but even for the places shutting out the UK travelers both business people and vacationers around the world.