CDC的原話

But as more and more countries experience community spread, successful containment at our borders becomes harder and harder.  Ultimately, we expect we will see community spread in this country.  It’s not so much a question of if this will happen anymore but rather more a question of exactly when this will happen and how many people in this country will have severe illness.  We will maintain for as long as practical a dual approach where we continue measures to contain this disease but also employ strategies to minimize the impact on our communities. 

https://www.cdc.gov/media/releases/2020/t0225-cdc-telebriefing-covid-19.html