Stop all incoming people who have been in China, or quarantine them all upon arrival.
NOW
What? Use common sense? That would be a first.
Stop AND quarantine. What else can you do? EIther release them and tell them to be careful, which is cosmically stupid, or deport them by sending them back on the flight on which they came. Which, is highly unsatisfactory for American citizens and their relatives.
Those US diplomats flying back likely consider themselves above quarantine.
too late
My Chinese renter arrived back after a month in China. She came in smiling and happy to see me and I think she was hurt when I asked her to stop about 8 feet away. At 81, I just don’t want to take chances. She said she and many others were wearing masks while waiting at the Chinese airport and while they were on the plane. She had not been near Wuhan.