World governments rushed to contain a new, heavily mutated COVID-19 strain Sunday, with Israel slamming its borders shut to foreign nationals and Australia reporting its first cases of the variant.
The variant now known as Omicron has cast doubt on global efforts to fight the pandemic because of fears that it is highly infectious, forcing countries to reimpose measures many had hoped were a thing of the past.
Scientists are racing to determine the threat posed by the heavily mutated strain, particularly whether it can evade existing vaccines.
Several countries have also announced plans to restrict travel from southern Africa, where it was first detected, including key travel hub Qatar, the United States, Britain, Saudi Arabia, Kuwait and the Netherlands.
The strictest among them is Israel, which said Sunday it would close its borders to all foreigners in a bid to curb the spread of the variant, just four weeks after reopening to tourists after a prolonged closure due to COVID.
"We are raising a red flag," Israeli Prime Minister Naftali Bennett said, adding the country would order 10 million PCR test kits to stem the "very dangerous" strain.
Israeli citizens will be required to present a negative PCR test and quarantine for three days if they have been vaccinated against the coronavirus and seven days if they have not, the prime minister's office said.
But the virus strain has already slipped through the net, and has now been found everywhere from the Netherlands to Hong Kong and Australia, where authorities Sunday said they had detected it for the first time in two passengers from southern Africa who were tested after flying into Sydney.
The arrival of the new variant comes just a month after Australia lifted a ban on citizens travelling overseas without permission, with the country's border also set to open to skilled workers and international students by the year's end.
Both cases were fully vaccinated, authorities said, and landed the same day that Canberra announced a sweeping ban on flights from nine southern African countries, including South Africa and Zimbabwe.
The speed at which governments slammed their borders shut took many by surprise, with travellers thronging Johannesburg international airport, desperate to squeeze onto the last flights to countries that had imposed sudden travel bans.
In the Netherlands, 61 passengers tested positive after arriving on two flights from South Africa in an ordeal one passenger described as "Dystopia Central Airline Hallway".
The New York Times global health reporter Stephanie Nolen said passengers, including babies and toddlers, were crammed together waiting to get tested, while "still 30 percent of people are wearing no mask or only over mouth".
Scientists in South Africa last week said that they had detected the new B.1.1.529 variant with at least 10 mutations, compared with three for Beta or two for Delta -- the strain that hit the global recovery hard and sent millions worldwide back into lockdown.
The variant has also revived geopolitical fault lines exacerbated by the pandemic, with the US quick to hail South Africa's openness about the new strain, a thinly-veiled jab at China's handling of information about the original outbreak.
Secretary of State Antony Blinken Saturday "praised South Africa's scientists for the quick identification of the Omicron variant and South Africa's government for its transparency in sharing this information, which should serve as a model for the world", a state department statement said.
But South Africa has complained it is being unfairly hit with "draconian" air travel bans for having first detected the strain, which the World Health Organization has termed a "variant of concern".
"Excellent science should be applauded and not punished," its foreign ministry said in a statement.
UK to enforce new Covid rules from Tuesday
Meanwhile, Britain's government on Sunday defended the pace and scale of its response to the new Omicron strain of COVID-19 against criticism that it was again falling behind the curve.
Health secretary Sajid Javid said mandatory mask-wearing will return to shops and public transport in England on Tuesday, and told families to plan for Christmas "as normal", despite new rules to combat the Omicron variant.
Also from Tuesday, all passengers arriving in Britain are being instructed to take a PCR test for Covid-19, and self-isolate until they register negative.
Prime Minister Boris Johnson had announced the tougher measures at a hastily arranged news conference on Saturday, but did not specify when they would take effect.
Johnson and other senior conservatives were widely criticised for his travel and quarantine policy earlier in the pandemic, when he kept borders open to foreign travellers even as infection rates spiralled, yielding Britain one of the world's worst per-capita death tolls from COVID.
The government controversially dropped the masks mandate in July for England, after a prior lockdown, but the devolved administrations in Scotland, Wales and Northern Ireland had kept it in place.
All four UK nations are expected to adopt the same PCR rule, after England again diverged in July by requiring only a simple lateral flow test for incoming passengers on flights, ships and trains.
Travel from 10 countries in southern Africa is now banned because of Omicron, but Javid conceded that hundreds of passengers had arrived on flights from South Africa on Friday without being tested.
But he told BBC television: "I think the speed at which we acted at could not have been any faster."
'Holes in the defences'
Javid ruled out reintroducing social distancing rules and work-from-home guidance, which were also controversially discarded in England earlier this year against the advice of government scientists.
Javid said it was too early to judge the effectiveness of existing vaccines against Omicron, as drugs manufacturers rush to research new treatments against the emergent strain.
But the government is seeking approval from its Joint Committee on Vaccination and Immunisation (JCVI) to expand the rollout of booster jabs, shortening the time-frame between second and third shots, and broadening the age range to all over-18s.
The JCVI is expected to respond early next week, Javid said.
He added that no further cases of Omicron had been detected in Britain, after the government on Saturday confirmed the first two cases, both linked to travel from southern Africa.
The Opposition Labour party said the government was again doing too little, too late after Omicron emerged.
Even after Tuesday, passengers can enter Britain without a pre-departure test and travel freely from their port of entry on public transport, Labour's foreign affairs spokeswoman Lisa Nandy said.
"We desperately want to see them tighten up the travel restrictions," she said on Sky News.
"There is a real problem when for 18 months the government has been warned that there are holes in those defences and still hasn't taken action to plug (them)."
Dutch find 13 new COVID variant cases among RSA passengers
Dutch health authorities said on Sunday they had found at least 13 cases of the new Omicron strain among 61 quarantined passengers who tested positive for coronavirus after arriving from South Africa. "The Omicron variant has so far been identified in 13 of the positive tests. The investigation has not yet been completed. The new variant may be found in more test samples," the National Institute for Public Health (RIVM) said in a statement.
Dutch authorities began testing for the Omicron variant after 61 out of 600 passengers on board two flights from South Africa to Amsterdam on Friday tested positive for COVID-19. Health minister Hugo de Jonge made an "urgent request" to people returning from southern Africa to get tested for Covid "as soon as possible".
"It is not unthinkable that there are more cases in the Netherlands," De Jonge told reporters. "Yes, we are concerned. But how much we don't know yet."
The minister added: "What is important now is that we keep our finger on the pulse, and keep up with the sequencing" of COVID tests to look for the new variant.
The positive cases are being kept in quarantine at a hotel near Amsterdam's Schiphol Airport.
Swiss voters back COVID-19 pass law
Also on Sunday, Swiss voters have firmly backed the law behind the country's COVID pass, according to projections following Sunday's referendum after an unusually tense and hostile campaign.
Shortly after the polls closed at noon (1100 GMT), market researchers GFS Bern, who conducted the main polling throughout the campaign, projected that 63 percent of voters had backed the "yes" vote.
The law provides the legal basis for the so-called COVID certificate, indicating that a person has been vaccinated or has recovered from the disease.
Opponents have said the certificate, which has been required since September for access to restaurants and other indoor spaces and activities, is creating an "apartheid" system.
As in much of Europe, Switzerland has seen growing anger over restrictions aimed at reining in the pandemic, and pressure to get vaccinated.
But in a country where referendums take place every few months in a climate of civility and measured debate, the soaring tensions around the vote came as a shock.
Police upped security around several politicians who have faced a flood of insults and even death threats.
In anticipation of protests at the results, police have fenced off the seat of government and parliament in Bern.
Observers warned that Sunday's vote could exacerbate tensions, and even spark a violent backlash from the losing side.
The campaign saw repeated protests, often led by the so-called "Freiheitstrychler", or "Freedom ringers" -- men dressed in white shirts embroidered with edelweiss flowers and with two large cowbells suspended from a yoke resting on their shoulders.
Some of the demonstrations led to violent clashes with police, who used rubber bullets and tear gas to rein in the crowds.
The referendum came as the worrying new COVID-19 variant Omicron, first detected in southern Africa and classified as a variant of concern by the World Health Organisation, has rattled countries and markets around the world.
Australia detects first Covid Omicron infections
Health officials said Sunday they had detected the Covid Omicron strain in Australia for the first time in two passengers who were tested after flying into Sydney from southern Africa.
The eastern state of New South Wales' health authority said it had conducted urgent genomic testing and confirmed the new strain was present in the two people who landed in Sydney on Saturday.
Both passengers came from southern Africa and arrived in Australia on a Qatar Airways flight via Doha, NSW Health said in a statement.
They tested positive for Covid shortly after arriving, leading to an urgent analysis for possible infection by the heavily mutated Omicron strain.
"The two positive cases, who were asymptomatic, are in isolation in the special health accommodation. Both people are fully vaccinated," NSW Health said.
Another 12 passengers from southern Africa on the same flight did not test positive for Covid but had been placed in quarantine, it said.
About 260 passengers and crew on the plane have also been told to isolate, the health authority said.
The plane with the infected passengers landed on the same day that Australia announced it was banning flights from nine southern African countries including South Africa and Zimbabwe.
The World Health Organization has listed Omicron as a variant of concern and said it could take several weeks to know if there are significant changes in transmissibility, severity or implications for Covid vaccines, tests and treatments.
The arrival of the new variant comes just a month after Australia lifted a ban on citizens travelling overseas without permission, with the country's border also set to open to skilled workers and international students by year's end.
After more than 18 months of closed borders, fully vaccinated Australian citizens no longer have to seek an exemption to leave the country. On 20 March last year Australia introduced some of the world's toughest border restrictions in response to the coronavirus pandemic.
For almost 600 days, countless international flights were grounded, and overseas travel slowed to a trickle.
Quarantine arrangements for returning vaccinated residents depend on where they arrive in Australia. While Sydney has scrapped quarantine for returning travellers, other Australian states with lower vaccination rates still have mandatory and costly 14-day hotel quarantine requirements.
It is unclear whether the arrival of the new variant will lead to a return to tighter rules. Speaking a few hours before the confirmation that the Omicron strain had arrived in Australia, New South Wales Premier Dominic Perrottet seemed reluctant to commit to any new restrictions.
"We need to learn to live alongside the virus and also live alongside the various strains of the virus that will come our way," Perrottet said. "The best thing that we can do is to get vaccinated and get booster shots," he added. "There are limits to what the state and federal government can do."
Angola shuts borders to regional neighbours over Omicron
Angola has become the first southern African country to suspend flights from its regional neighbours in a bid to prevent the spread of the Omicron variant of the coronvirus, its national airline said.
A long list of countries have shut their borders to the region since South African scientists announced the new coronavirus variant last week.
Angola's state-owned TAAG airline on Saturday said it would suspend all flights to Mozambique, Namibia and South Africa from Sunday until further notice.
The suspension is in compliance with the government's decision to temporarily ban air links to Botswana, Eswatini, Lesotho, Mozambique, Namibia, South Africa and Zimbabwe, it said in a statement.
Angola itself was placed on the UK's red travel list over concerns about Omicron last week.
Known as B.1.1.529, South African scientists announced its discovery on November 25, blaming it for a resurgence in cases in the continent's worst-hit country.
With multiple mutations, Omicron is thought to be highly contagious and resistant to immunity, although its ability to evade vaccines is still being assessed.
The World Health Organisation has designated it a variant of concern.
While many Western and Asian countries rushed to enforce travel bans, most African nations have kept their borders open for the time being.
Angola is one a few to have shut doors, along with Mauritius, Morocco and the Seychelles.
With inputs from agencies