Trump and Pence have so far had three exposures to people who tested positive shortly after the contact, at least. Hopefully, Speaker Pelosi is holing up in a secure location so she can step in as President.

In China public health authorities watched surveillance video of a public bus to see the interactions between people who contracted the virus. One person sitting 4.5 meters behind the vector got it. One person who entered the bus 30 minutes after the vector left got it. This tells you that the 2.5 meter "safety" distance is inadequate. It also tells you public transit is very dangerous because the virus circulates in the enclosed air and remains on surfaces. That would include trains and airplanes.

The most obvious control measure is to shut down flights immediately, and have everybody isolates in place. Some countries did that. US and UK did not.

CNN reports that Trump is worried about the last exposure, when the Brazilan President and his infected spokesman were in a room at Mir-A-Lago with Trump and Pence for quite a while. Lindsey Graham and some other Republican congressmen were there as well.