RELATED: Virus Experts Just Gave This New COVID Warning—Even If You’re Vaccinated. The BA.2 variant, also colloquially referred to as the Omicron stealth sub-variant, is spreading worldwide right now. This includes in the U.S., where the White House says it has been circulating for some time now. “We currently have about 35,000 cases [of the BA.2 variant] in this country. We expect some fluctuation, especially at this relatively low level, and, certainly, that to increase,” Press Secretary Jen Psaki said during a March 14 press briefing. According to Psaki, the stealth Omicron sub-variant is also more transmissible than the original. While the U.S. is still experiencing a decline in COVID numbers, not all countries are having the same luck. According to CNN, cases and hospitalizations in the U.K. are climbing once again just two weeks after the country dropped its isolation requirement for people who test positive. U.K. infections were up by 48 percent last week compared to the week prior, while hospitalizations went up 17 percent over the same time period. And it’s not just the U.K. CNN reported that COVID infections are rising in more than half of the countries in the European Union (EU) right now. In the Netherlands, daily cases have risen 48 percent in the last week, while Germany has also seen a 20 percent increase, per data from Johns Hopkins University. Anthony Fauci, MD, a top White House COVID adviser, told CNN that a combination of the more transmissible BA.2 variant, the opening of society, and waning immunity from vaccination or prior infection is contributing to the rise in COVID numbers for these countries. RELATED: For more up-to-date information, sign up for our daily newsletter. According to the CDC, the BA.2 variant is currently estimated to be causing nearly 12 percent of new COVID cases in the U.S. Meanwhile, in the U.K. and other European countries where cases are rising again, the sub-variant is accounting for more than 50 percent of new infections. “The tipping point seems to be right around 50 percent,” Keri Althoff, PhD, an epidemiologist at Johns Hopkins Bloomberg School of Public Health, told CNN. “That’s when we really start to see that variant flex its power in the population.” Althoff says that the worst case scenario for the next phase of the COVID pandemic in the U.S. is that the BA.2 variant starts to surge here as soon as immunity from the currently dominant Omicron variant falls. It took about a month for the sub-variant to overpower the original variant in the Netherlands, she said. If we compare that same timeline to the current U.S. situation, that means that the BA.2 variant would surge at the same time the immunity conferred by winter’s Omicron infections starts to drop, CNN reported. “I’m concerned about that,” Althoff admitted to the news outlet. “We were in a similar situation last spring, where we really got hopeful that things were going to settle down, and we got a little bit of a summer, and then we got walloped by Delta.“ae0fcc31ae342fd3a1346ebb1f342fcb Despite uncertainty on the horizon, mask requirements and vaccine mandates have been lifted across the country over the last few weeks. But while there is a strong desire to go back to normal as COVID cases are falling, it’s a delicate balance, experts stress. “Without a doubt, opening up society and having people mingle indoors is clearly something that is a contributor [to cases rising in Europe], as well as overall waning immunity, which means we’ve really got to stay heads-up and keep our eye on the pattern here,” Fauci told CNN. “So that’s the reason why we’re watching this very carefully.” Other experts say certain protection measures are still important right now. This includes simply getting more people vaccinated. According to the CDC, about 35 percent of the eligible population have still not been fully vaccinated and 24 percent haven’t even gotten one dose. And if things start to go south with the new variant, this might not be the only mitigation measure we’ll need to keep up with. “The important thing in this massive experiment where we’re dropping all masking and restrictions is we have to stay diligent in terms of monitoring of it and testing and be prepared to possibly reverse a lot of the relaxing of these restrictions,” Deborah Fuller, PhD, a microbiologist at the University of Washington, told CNN. “We can’t let our guard down, because the message that people get when they say ‘we’re lifting restrictions’ is the pandemic is over. And it’s not.” RELATED: Dr. Fauci Says This Is Now the “Best Case Scenario” for Ending COVID.