The highly contagious delta variant now accounts for more than 93% of new COVID-19 infections in the United States, according to data from the Centers for Disease Control and Prevention. 

The spread of the variant, along with lagging vaccination rates, has reversed much of the progress the U.S. had made after vaccines began to hit the market late last year. 

The country’s seven-day average for new COVID-19 cases overall as of Monday was 84,389, the highest it has been since Feb. 14. The number of Americans hospitalized with the virus is at its highest point since late February, and deaths are rising again as well — up to 354 a day.

Last week, the CDC said the delta variant, which was first detected in India, is likely more severe than earlier strains and is about as transmissible as the chickenpox. The CDC said each infected person spreads the virus on average to eight or nine others — the original COVID-19 strain was passed to two people on average. And fully vaccinated people with breakthrough cases are just as likely to transmit the virus as an unvaccinated people, according to the public health agency.

The 93% number also includes sublineages of the delta variant, all of which are classified as variants of concern.

In some states, including Iowa, Kansas, Missouri and Nebraska, delta accounts for 98% of new cases.

Delta has quickly become by far the most dominant COVID-19 strain spreading around the country. In the two weeks ending May 22, it made up just 3.1% of cases in the U.S. Back then, the alpha variant, first detected in the United Kingdom, was the country’s dominant strain, accounting for 69% of the country’s infections.  Now it makes up less than 3%.