Not that this ban makes a lot of sense, but not including the UK makes even less sense, considering they've already reported 400 cases (compared to the ~1,200 in the U.S.)

edit: to be fair, maybe the administration would've preferred to just ban travel from Italy. But I'm guessing it's not possible to restrict travel from just one member of the EU.

The ban is for people who have been in the Schengen zone within the last 14 days, not just for direct arrivals from those states.

UK is already a hotspot. 100 confirmed cases in London (as of 11 Mar) means we should expect 10x that in practice. They just started later than some other countries.