The COVID-19 strain known as the Delta variant, or the B.1.617.2 strain, first detected in India, could become the dominant strain in the U.S. by fall 2021, said Dr. Scott Gottlieb, the former head of the Food and Drug Administration. 

"And I think the risk is really to the fall that this could spike a new epidemic heading into the fall," Gottlieb told in a CBS interview on Sunday.