Delta variant accounts for 83% of US COVID-19 cases, CDC says

The delta variant of the coronavirus now accounts for an estimated 83% of COVID-19 cases in the United States as it continues to surge largely among unvaccinated populations, officials said. 

The percentage is a dramatic increase from the week of July 3, when the highly transmissible variant accounted for about 50% of genetically sequenced coronavirus cases.

"In some parts of the country, the percentage is even higher — particularly in areas of low vaccination rates," Dr. Rochelle Walensky, director of the Centers for Disease Control and Prevention, said during a U.S. Senate hearing on Tuesday.

Walensky noted the large reductions in COVID-19 cases, hospitalizations and deaths in the U.S. since peaking in January, adding that such trends "are a testament to the success of our vaccination program."

"The best way to prevent the spread of COVID-19 variants is to prevent the spread of disease, and vaccination is the most powerful tool we have," she continued. 


Director of the Centers for Disease Control and Prevention Rochelle Walensky listens during the Senate Health, Education, Labor, and Pensions Committee hearing on Capitol Hill in Washington, D.C. on July 20, 2021. (Photo by STEFANI REYNOLDS/POOL/AFP

The delta variant is a mutated coronavirus that spreads more easily than other versions. It was first detected earlier this year in India but now has been identified in countries around the world.

Walensky stressed that the CDC’s available data indicates that the COVID-19 vaccines currently being administered in the U.S. provide protection against severe disease, hospitalizations and death. The U.S. averaged 239 deaths per day last week, an increase of nearly 48% over the week prior, she said.

"We know that the majority of these deaths could be prevented with a simple, safe, available vaccine," Walensky said.

To date, 48.6% of the total U.S. population is fully vaccinated, including nearly 60% of American adults, CDC data shows

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This story was reported from Cincinnati. The Associated Press contributed.