WASHINGTON • With coronavirus cases rising in parts of Europe and Asia, scientists worry that an extra-contagious version of the omicron variant might soon push cases up in the United States, too.

Experts are also keeping their eyes on another mutant: a rare delta-omicron hybrid that they say doesn’t pose much of a threat right now but shows how wily the coronavirus can be.

The U.S. will likely see an uptick in cases caused by the omicron descendant BA.2 starting in the next few weeks, said Dr. Eric Topol, head of Scripps Research Translational Institute.

“It’s inevitable we will see a BA.2 wave here,” he said.

One reason? After about two months of falling COVID-19 cases, pandemic restrictions have been lifted across the U.S. Many people are taking off their masks and returning to indoor spaces like restaurants and theaters.

Dr. Anthony Fauci, the U.S. government’s top infectious disease expert, told ABC’s “This Week” over the weekend that he also thinks the U.S. will likely face an “uptick” similar to what’s happening in Europe, particularly the United Kingdom, where BA.2 is the dominant strain. He said he doesn’t think it will be a “surge.”

The U.K. has “had the same situation as we’ve had now,” Fauci said. “They have BA.2. They have a relaxation of some restrictions such as indoor masking and there’s a waning of immunity” from vaccines and past infections. In the U.S., the latest data from the Centers for Disease Control and Prevention shows overall COVID-19 cases have been trending down.