WASHINGTON, Nov 29 — Americans should prepare to eventually encounter the new Omicron Covid-19 variant, but US health officials yesterday said the travel ban starting today on most travellers from southern Africa should help buy time to assess any new risk.

"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.”

Omicron, which was first detected in southern Africa, has now been confirmed in Australia, Belgium, Botswana, Britain, Denmark, Germany, Hong Kong, Israel, Italy, the Netherlands, South Africa, and the United States’ neighbour to the north, Canada.

US President Joe Biden, returning to Washington following the Thanksgiving holiday weekend, said he would meet with his Covid-19 response team yesterday afternoon and have more to say later.

US health officials will also speak with counterparts in South Africa yesterday to get "more information in real time,” Fauci told NBC, adding 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 said on NBC’s "Meet the Press.”

Fauci told ABC it was too early to know whether new lockdowns or mandates are needed.

"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,” he added on NBC.

Potentially more contagious than previous variants, Omicron has sparked worries worldwide and rattled markets.

Health officials in Canada confirmed yesterday they had detected two cases of the Omicron variant of the virus among two people who recently travelled to Nigeria.

Its appearance in the United States, where 30 per cent of the population has not gotten a single dose of vaccine, could threaten to undermine the nation’s recovery nearly two years after Covid-19’s emergence and further pressure local healthcare systems already taxed by the recent Delta variant.

Rising cases as colder weather forces more people indoors has also caused some hospital systems and US states, including New York, to declare emergencies.

So far, nearly 782,000 people have died in the United States from Covid-19 since early 2020, the most of any country in the world, amid over 48 million infections, Reuters data show.

Travellers banned, not flights

The United States is joining other nations in seeking to block transmission by imposing travel restrictions.

Beginning at 12.01am ET (0501 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. US citizens who have travelled to the countries will still be able to enter the United States.

A union representing drivers for ridesharing apps welcomed the restrictions. "Putting a pause on some international travel could save countless lives and it’s welcome news to the frontline Uber and Lyft drivers who transport international travellers arriving in US cities,” Brendan Sexton, executive director of the Independent Drivers Guild, said in a statement.

Flights by Delta Air Lines and United Airlines have continued from South Africa to the United States since the variant was discovered. Passengers interviewed by CNN as they arrived on flights from southern Africa at two US airports — one in Atlanta and the other at Newark — said they were not subject to any specific checks or restrictions.

Fauci and other top officials said the sudden burst of cases made Omicron worrisome and it remained unclear how current vaccines or therapeutics could be impacted.

"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 Dr Francis Collins told Fox News Sunday.

Vaccine makers Pfizer/BioNTech and Moderna have said they expect more information soon.

"We have to go through a couple of weeks yet of uncertainty,” Moderna Chief Medical Officer Dr Paul Burton told CNN, saying Omicron’s transmissibility and severity were also still unknown along with current vaccines’ effectiveness against it.

‘Clarion call’ for shots

Fauci pressed Americans to continue to get Covid-19 vaccines and boosters while experts evaluate Omicron.

"This is a clarion call...(to) get vaccinated,” he told NBC.

White House chief of staff Ron Klain echoed that sentiment, saying on Twitter: "The thing every vaccinated adult should do now, if they have not done it yet, is get a booster shot.”

The United States has recorded over 1.1 million new Covid-19 cases in the last 14 days, up 9 per cent from the prior two weeks, Reuters data shows, with Michigan and Minnesota leading the nation in new cases, based on infections per 100,000 residents.

The governor of one hard-hit state, Arkansas’ Asa Hutchinson, expressed worry over another blow from the latest variant, telling CNN’s "State of the Union” programme: "Delta has been tough on us. And so we don’t welcome a new variant. And it is a great concern.”

The variant could cast a pall over the rest of the US holiday season and potentially impact companies’ return-to-office plans depending on what officials discover in coming weeks. A number of banks and other firms have said they planned for workers to come back in January.

On Wall Street, sources at major US banks and European banks with large US operations said they were not yet changing their policies but were monitoring the situation. — Reuters