By mid-2021, delta had replaced alpha as the most common COVID-19 variant in the US
In early May 2021, several variants of the SARS-CoV-2 coronavirus were circulating in the U.S., with the alpha strain dominant by far. In June, the delta strain began spreading more quickly, and by the end of July was responsible for 93% of all COVID-19 cases in the U.S.
An area chart showing the percentage of COVID-19 cases caused by each variant of the coronavirus from May through July 2021.
