The delta coronavirus variant, first identified in India, is now the most commonly circulating strain in the U.S., according to sequencing data cited by The Wall Street Journal.
As of June 27, the strain accounted for about 40 percent of positive COVID-19 test samples, according to the population genomics company Helix, which is contracted with the CDC to track variants. The variant accounted for 26.1 percent of all U.S. cases in the two weeks ending June 19, according to CDC estimates.
"This is the first time we felt confident to say that Delta is the most prevalent lineage in the U.S.," William Lee, PhD, Helix’s vice president of science, told the Journal.
Dr. Lee projects the variant will account for at least half of all COVID-19 cases in the U.S. by early to mid-July.
The CDC on June 30 said it is maintaining current masking guidelines — which say fully vaccinated people don't need them in most cases — amid the delta variant's rising prevalence.
"People who are fully vaccinated are protected, including from the variants currently circulating in the country such as the delta variant," the CDC said in a statement cited by the Journal.