. People enter the baggage claim area from the international arrivals terminal as the U.S. reopens air and land borders to coronavirus disease (COVID-19) vaccinated travellers for the first time since the COVID-19 restrictions were imposed, at SBy Susan Heavey WASHINGTON U.S. health officials on Sunday said they were preparing for the likely appearance of the new Omicron COVID-19 variant, with restrictions set to begin on Monday against travelers from eight southern African countries. "Inevitably, it will be here," although no cases have been detected yet, the nation's top infectious disease official, Dr. Anthony Fauci, told ABC News' "This Week." He added that U.S. health officials would speak with their counterparts in South Africa later on Sunday, saying the flight curbs would give them more time to gather information and weigh possible action. It "is to get us better prepared, to rev up on the vaccination, to be really ready for something that may not actually be a big deal, but we want to make sure that we're prepared for the worst," he separately told NBC News' "Meet the Press" program. The new Omicron coronavirus variant, first discovered in South Africa -pharmaceuticals/japan-tighten-border-controls-s-africa-others-new-virus-variant-jiji-2021-11-26 and announced in recent days, has already been detected in a growing number of countries. The United States must do "anything and everything" amid likely cases of the variant but it is "too early to say" whether new lockdowns or mandates are needed, Fauci added on ABC. Potentially more contagious -worried-should-we-be-about-omicron-variant-2021-11-27 than previous variants, Omicron has sparked worries worldwide, rattling markets and public-health experts who have long warned about ongoing changes to the novel coronavirus amid the race to vaccinate against it. "It clearly is giving indication that it has the capability of transmitting rapidly. That's the thing that's causing us now to be concerned," Fauci said on "Meet the Press." Its appearance stateside could threaten to undermine the nation's recovery nearly two years after COVID-19's emergence and further pressure local healthcare systems that have already felt the weight of the recent Delta variant. Rising cases as colder weather forces more people indoors amid ongoing vaccine hesitancy that has left many people in some U.S. regions unprotected has also forced some hospital systems and U.S. states, including New York, to declare emergencies. So far, 781,797 people have died in the United States from COVID since early 2020, the most of any country in the world, amid 48,288,375 infections, data show. U.S. President Joe Biden, due to arrive back in Washington later on Sunday following the Thanksgiving holiday weekend, has said he is being briefed on the variant. Meanwhile, the United States is joining other nations in seeking to block transmission by imposing travel restrictions. Beginning at 12:01 a.m. ET (0500 GMT) on Monday, it will bar entry of nearly all foreign nationals who have been in any of eight southern African countries within the last 14 days and has warned Americans against traveling to those nations. Still, Delta Air Lines (NYSE:DAL) and United Airlines have said they are not planning any changes to their South Africa-U.S. routes despite the Biden administration's curbs. It was not immediately clear what additional steps travelers may face coming from the region as flights continued over the weekend. Fauci and other top officials said the sudden burst of cases made Omicron worrisome, but it was not yet clear how current vaccines or therapeutics would be impacted. Vaccine makers Pfizer/BioNTech and Moderna (NASDAQ:MRNA) have said they expect more information soon. "We need more data there before we can say confidently that this is not a severe version of the virus but we should find that out in the next couple weeks," outgoing National Institutes of Health Director Francis Collins told "Fox News Sunday." Fauci pressed Americans to continue get COVID-19 vaccines and boosters while experts evaluate Omicron. "This is a clarion call...(to) get vaccinated," he told NBC.