The Delta variant of coronavirus now accounts for 26% of Covid-19 cases in the US, the US Centers for Disease Control and Prevention estimates.
The CDC updated its estimates of which variants are circulating on Tuesday.
The B.1.1.7 or Alpha lineage of the virus, first spotted in the UK, was still the dominant variant in the US as of June 19, representing 47.8% of cases, the CDC estimated.
But it said the B.1.617.2 or Delta variant first seen in India was now the second most common lineage, making up 26.1% of cases. The CDC bases its estimates on genomic sequencing of samples taken from people and then models what that might mean for the whole country.
The P.1 or Gamma variant first seen in Brazil is the third most common variant in the US, accounting for 14.5% of cases as of June 19.