A traveler walks into an entrance at Ronald Reagan Washington National Airport in Arlington, Virginia, the United States, April 14, 2022. (Photo by Ting Shen/Xinhua)

The new strain, called BA.2.12.1, makes up about a fifth of new COVID-19 cases in the United States, according to data released Tuesday by the CDC.

While Omicron subvariant BA.2 remains the dominant strain in the United States, a new subvariant is gaining its foothold in the country, according to the latest data of the U.S. Centers for Disease Control and Prevention (CDC).

The new strain, called BA.2.12.1, makes up about a fifth of new COVID-19 cases in the country, according to data released Tuesday by the CDC.

The data increased from 11.4 percent a week before, and 6.9 percent two weeks prior, CDC data showed.

The majority of COVID-19 cases in the United States -- around 75 percent -- are still caused by BA.2., which has become the country's dominant variant since late March.

But BA.2.12.1, along with another subvariant of Omicron, called BA.2.12, contributed to the recent spike in COVID-19 cases in New York State, according to the State Department of Health.

Both variants are sub-lineages of BA.2, which now accounts for 80.6 percent of COVID-19 infections in New York. The subvariants have been estimated to have a 23 percent to 27 percent growth advantage above the original BA.2 variant, said the New York State Department of Health.

The United States is now averaging about 35,000 new infections daily, up 19 percent from the previous week and 42 percent from two weeks prior, CDC data show.

Meanwhile, about 370 new deaths and 1,400 new hospitalizations were reported across the country every day.

Health experts said new COVID-19 cases are increasingly undercounted with the rise of at-home testing.

Less than a week after the CDC extended mask requirement on airplanes, trains, buses and other public transportation to prevent the surge in COVID-19 cases, federal judge in Florida struck down the mask mandate on Monday.

Several airlines have dropped their mask rule for domestic flights after the federal judge voided the mandate.

Pulling back on the travel mask requirement at this moment is "very, very concerning," Saskia Popescu, an infectious disease epidemiologist and assistant professor at George Mason University, told The New York Times.

"We're definitely starting to see a trend up in cases," she said. "My concern is that we may see what happened in the U.K., where they drastically pulled back restrictions and saw a significant surge, and this will contribute to rising numbers."