• U.S. health experts are warning a highly contagious Covid omicron variant, called BA.2, could soon lead to another uptick in domestic coronavirus cases.
• Officials such as White House chief medical advisor Dr. Anthony Fauci say BA.2 is about 50% to 60% more transmissible than omicron, but it does not appear to be more severe.
• The variant is estimated to account for about 25% or 30% of new cases in the U.S.

U.S. health experts are warning an emerging, highly contagious Covid omicron variant, called BA.2, could soon lead to another uptick in domestic coronavirus cases.

White House chief medical advisor Dr. Anthony Fauci said BA.2 is about 50% to 60% more transmissible than omicron, but it does not appear to be more severe. Health officials continue to stress coronavirus vaccines and boosters remain the best ways to prevent serious illness from the virus.

"It does have increased transmission capability," Fauci said Sunday on ABC's "This Week." "However, when you look at the cases, they do not appear to be any more severe and they do not appear to evade immune responses either from vaccines or prior infections."

The variant has already caused cases to increase in China and parts of Europe. It is estimated to account for about 25% or 30% of new cases in the U.S., but it could become the country's most dominant variant, Fauci said.

Fauci said he expects "an uptick in cases" due to BA.2, but not necessarily a massive surge like other variants have caused. That's despite the Centers for Disease Control and Prevention recently relaxing mask recommendations for most Americans.

U.S. Surgeon General Vivek Murthy and Dr. Scott Gottlieb, a board member of Covid vaccine maker Pfizer and a former head of the Food and Drug Administration, also expressed similar views on Sunday regarding BA.2.

Murthy said the variant could cause a new spike in cases but that the country is in a better position now than it was in the previous two years, when Covid-19 "defined our lives."

"We should be prepared, Covid hasn't gone away," Murthy said during "Fox News Sunday." "Our focus should be on preparation, not on panic."

Gottlieb, echoing previous comments days before to CNBC, said he also expects "some uptick" due to BA.2 but "not a big wave of infection."

"I think we're going to continue to see low levels of infection through the summer. But before we get there, we're probably going to see some tick-up of infection like the Europeans are seeing right now, maybe not as pronounced," Gottlieb said Sunday during CBS's "Face the Nation."

The CDC reported more than 31,200 new Covid-19 cases Saturday, including 958 deaths. Both are significantly down from the beginning of the year.

Disclosure: Scott Gottlieb is a CNBC contributor and is a member of the boards of Pfizer, genetic testing start-up Tempus, health-care tech company Aetion and biotech company Illumina. He also serves as co-chair of Norwegian Cruise Line Holdings' and Royal Caribbean's "Healthy Sail Panel."