By Emily Anthes
Published July 7, 2021
Updated July 14, 2021
The highly contagious Delta variant of the coronavirus is now the dominant variant in the United States, accounting for 51.7 percent of infections, according to new estimates from the Centers for Disease Control and Prevention.

As health officials had expected, the Delta variant has rapidly overtaken Alpha, the variant that spread through the United States this spring. Alpha, first detected in Britain, now makes up just 28.7 percent of infections, according to the C.D.C.

Still, overall, the average numbers of new virus cases and deaths across the country, as well as hospitalizations, are significantly down from the devastating peaks during previous national surges.

Delta was first detected in India. Research suggests that most vaccines still provide good protection against it and remain highly effective at preventing hospitalizations and deaths.

In England, for instance, where the variant now causes almost all infections, case numbers have risen sharply in recent weeks, but hospitalization rates have increased more slowly and remain low. Next week, a final decision will be made about whether to lift most remaining restrictions in England, including mask rules, on July 19