Confirmed or suspected cases of the new Covid variant have already emerged in several European countries, as well as in Israel and Hong Kong, just days after it was identified by researchers in South Africa.
World governments have rushed to contain a new, heavily mutated Covid-19 strain, known as Omicron, as they shut their borders and announce travel curbs.
Several countries announced plans on Sunday 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 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-19.
"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.
Omicron spreading fast
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 said on Sunday they had detected it for the first time in two passengers from southern Africa who were tested after flying into Sydney.
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".
Dutch Health Minister said on Sunday there are possibly more cases of the Omicron variant in the Netherlands.
In Australia, the arrival of the new variant comes just a month after the country 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.
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.
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.