Here are some facts I picked up from trusted sites.
The Wall Street Journal reported that all travelers, including US citizens, will need to provide proof of a negative coronavirus test. This will happen on January 26, most likely. This is a directive from the Centers for Disease Control and Prevention.
Airlines must confirm the negative test for passengers prior to boarding. Those with the correct documentation will be allowed to board. If you do not have this, you will be denied boarding flights to the US.
This test must be within three days of the departure date.
If you have recovered from COVID-19, you will need documentation of that.
The CDC also recommends travelers get tested again three to five days after returning home, as well as quarantine for seven days after travel.
Of course, this does not eliminate all risk. It is one more step combined with staying at home, wearing masks, and social distancing.