CDC director says Delta variant is responsible for 83% of all new sequenced COVID-19 cases

• The Delta variant of the coronavirus now accounts for an estimated 83% of all new sequenced COVID-19 cases in the US, the CDC director said.
• The CDC's Rochelle Walensky testified during a Senate hearing on the coronavirus pandemic Monday.
• "This is a dramatic increase up from 50% the week of July 3," Walensky said.
• See more stories on Insider's business page.

The highly transmissible Delta variant of the coronavirus now accounts for an estimated 83% of all new sequenced COVID-19 cases in the United States, the head of the Centers for Disease Control and Prevention said Tuesday.

CDC director Rochelle Walensky gave the updated statistic as she testified during a Senate hearing on the coronavirus pandemic and the federal government's response.

The CDC has "released estimates of variants across the country and predicted the Delta variant now represents 83% of sequenced cases," Walensky testified, adding, "This is a dramatic increase up from 50% the week of July 3."

"In some parts of the country the percentage is even higher, particiualry in areas with low vaccination rates," Walensky said.

About 161.5 million people in the nation or 48.6% of the US population is now fully vaccinated against the coronavirus, according to CDC data. More than 56% of the population has receieved at least one vaccine dose.

But Walensky explained that the country's vaccination progress across the country "is not uniform."

"Vaccine coverage varies by state and by county. Communities where people remain unvacccinated are most vulnerable and are most likely to experience increase in case counts," she said.

Additionally, Walensky testified, in areas where vaccination is low, coronavirus cases and related hospitalizations have ticked up.

"Over the last week we have averaged 239 deaths per day, an increase of nearly 48% over the prior week," she said.

Walensky continued, "Each death is tragic and even more heartbreaking when we know that the majority of these deaths could be prevented with a simple safe available vaccine."

Areas with "limited vaccination coverage," Walensky said, "are allowing for the emergence and rapid spread of the highly transmissible Delta variant."