The delta variant, a highly contagious strain of COVID-19 first detected in India, now makes up approximately 83% of coronavirus cases nationwide, according to the U.S. Centers for Disease Control and Prevention. 


What You Need To Know

  • CDC Director Dr. Rochelle Walensky on Tuesday said the highly contagious delta variant now makes up 83% of sequenced COVID-19 cases nationwide

  • Walensky said the number is a “dramatic increase” from the week of July 3, when the delta variant made up nearly 50% of sequenced cases nationwide

  • In some parts of the country, where vaccination rates have lagged, the incidence rate of the delta variant is even higher

  • Walensky and Dr. Anthony Fauci are testifying in front of the Senate Health Committee on Tuesday

In testimony before the Senate Health Committee, CDC Director Dr. Rochelle Walensky said the number is a “dramatic increase” from the week of July 3, when the delta variant made up nearly 50% of sequenced cases nationwide.

In parts of the country where vaccination rates have lagged, the percentage is even higher, Walensky noted. 

“The message from CDC remains clear: 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 told Senators on Tuesday. “We must continue to expand vaccine coverage by building trust and confidence in COVID-19 vaccines.” 

Walensky added that the “overwhelming majority” of COVID-19 deaths are occuring in the unvaccinated population.  

Dr. Anthony Fauci, the nation’s leading infectious disease expert, also testified in front of the committee on Tuesday, saying of the delta variant: “The reason it's so formidable is the fact that it has the capability of transmitting efficiently from human to human in an extraordinary manner well beyond any of the other variants that we've experienced up to now.”

To date, the delta variant has been detected in at least 90 countries across the world.

This is a developing story. Please check back for updates.