Experts fear that COVID-19 cases in the United States will rise in the next few weeks as the new BA.2 variant continues to spread.

Data from the Centers for Disease Control and Prevention shows BA.2, which is a subvariant of omicron, has been tripling in prevalence every two weeks.

As of the week ending March 11, BA.2 makes up 23.1% of all COVID cases in the U.S. compared to 7.1% of all cases the week ending Feb. 26, according to the CDC.

Although the original omicron variant still makes up the majority of America’s COVID infections, its prevalence has dropped over the same period, from 74.5% to 66.1%.

Dr. Anthony Fauci, the nation’s top infectious disease expert, said given the growing prevalence of BA.2, he expects cases will increase within the next month.

“I would expect that we might see an uptick in cases here in the United States because, only a week or so ago, the CDC came out with their modification of the metrics for what would be recommended for masking indoors, and much of the country right now is in that zone, where masking indoors is not required,” Fauci told ABC affiliate KGTV Wednesday.

Fauci added that he believes BA.2 will become the dominant variant in the country, surpassing the original omicron variant.

Several European countries — such as Finland, France, Germany, the Netherlands and the United Kingdom — have reported a spike in COVID-19 over the last couple of weeks.

In the U.K., 93,943 cases were recorded Wednesday, according to Johns Hopkins University, more than double the 45,303 recorded two weeks earlier.

“Europe has been an important sign of what we can expect in the U.S.,” said Dr. John Brownstein, an epidemiologist at Boston Children’s Hospital and an ABC News contributor. “Rising infections, an increase in variant prevalence and a slow booster rollout is likely a sign of a surge. Whether it will be another wave or small bump, we don’t know yet.”

Last month, U.K. Prime Minister Boris Johnson announced any remaining COVID-19 measures in England would be dropped so the country could move into a new phase of the pandemic, which he described as “living with COVID.”

Several European countries followed suit, as did the U.S., which eased masking guidance for 70% of the country, including for schools.

Fauci said he is encouraged that BA.2 does not appear to cause more severe disease, but warned if the U.S. experiences another COVID wave, Americans must be willing to readopt mitigation measures — and other experts agree.

“What we’re seeing now is the importance of being able to off-ramp interventions as cases up and how they need to readopted as they come back,” Brownstein said. “This might mean masking in certain setting and spending less time in indoor settings and environments we know the virus can spread quickly.”

Dr. Ali Mokdad, an epidemiologist with the University of Washington’s Institute for Health Metrics and Evaluation in Seattle, said he hopes that the U.S. government also has a plan to distribute COVID-19 antivirals in case of a surge.

“These medications are life-savers and if someone is diagnosed early on and they take these antiviral medications, they’re not going to end up in the hospital and die from it,” he told ABC News. “So it will really reduce the burden of COVID-19.”

ABC News’ Arielle Mitropoulos contributed to this report.