AMSTERDAM (NYTIMES) - As more countries placed travel bans on southern Africa early on Saturday (Nov 27) for fear of a new and possibly more dangerous variant of the coronavirus, passengers on two flights from South Africa found themselves caught in a pandemic nightmare.

After about 30 hours squeezed together in the planes, crammed buses and then in waiting rooms, 61 of the more than 500 passengers on those flights had tested positive and been quarantined.

They were being checked for Omicron, named by the World Health Organisation last Friday as a "variant of concern", its most serious category.

Everyone else, according to Ms Stephanie Nolen, The New York Times' global health reporter, who was on one of the planes, "has scattered to the world".

The chaos in Amsterdam seemed emblematic of the varied, and often scattershot, responses to the virus across the world, with masking rules, national testing requirements and vaccine mandates differing from country to country and continent to continent.

KLM Royal Dutch Airlines, the carrier operating the flights, said only some passengers had to show proof of a recent negative test, depending on vaccination status and the requirements of their final destination.

Such gaps could open avenues for contagion, especially for a potentially threatening new variant.

"That number of people seems like a very high number to have this happen," said Dr Andrew Pekosz, a public health researcher from Johns Hopkins University. "Unless there's really tremendous amounts of spread of this virus locally that was not detected."

The Omicron variant is likely to be found in some of those 61 passengers who tested positive, Dutch public health officials announced on Saturday. The sequencing is still being performed by the Dutch agency for disease control and prevention.

It was unclear how many passengers may have tested positive for the variant.

Those who tested positive for the coronavirus at Amsterdam's Schiphol Airport last Friday have been transferred to quarantine hotels. Those who tested negative could continue their journey or, if the Netherlands was their final destination, were told to quarantine at home.

The government is also telling thousands of people who have returned from southern Africa in the past few days to get tested, even if they do not have symptoms.

There is still relatively little known about Omicron. It has mutations that scientists fear could make it more infectious and less susceptible to vaccines - although neither of these effects is yet to be established.

On Saturday, fear of Omicron arrived nonetheless, as officials in Britain reported two cases of the variant, and Germany and the Czech Republic investigated suspected cases.

The numbers of confirmed cases outside southern Africa remain small, but there are worries the virus could have spread more widely before scientists there discovered it.

"It would be irresponsible" not to be worried about the new variant, Mr Roberto Speranza, health minister of Italy, the first European Union nation to block flights from southern Africa, told the Corriere della Sera newspaper on Saturday.

"It's a new and worrying element," he said.

After the initial shock of the discovery of a case of the Omicron variant in Europe last Friday in Belgium, European leaders, already struggling with a surge in cases that has made it once again the epicentre of the pandemic, tried to strike a balance between increasing caution and avoiding panic. But the virus would not cooperate.

Last Friday evening, Dr Ursula von der Leyen, president of the European Commission, the EU's executive arm, said on Twitter she held fruitful conversations with the pharmaceutical companies and that they "explained their efforts to quickly and thoroughly understand the Omicron variant and adjust our strategies accordingly. Time is of the essence".

The EU acted with rare unity in response to the threat posed by the new variant, binding together to restrict travel to and from southern Africa.

Ms Vivian Loonela, a spokesman for the commission, said on Saturday that "member states agreed to introduce rapidly restrictions on all travel into the EU from seven countries in the southern Africa region - Botswana, Eswatini, Lesotho, Mozambique, Namibia, South Africa, Zimbabwe".

Mr Speranza told Corriere della Sera newspaper that he considered it wise "to activate the emergency brake", adding that the "European coordination on these decisions is fundamental".

One of Mr Speranza's main criticisms during the first wave of the virus back in 2020 was that Italy was left alone, and that France, Britain and other countries did not act to ban flights from China as Italy did in January of that year.

He said the strategy of the government - to promote vaccinations through a strict health pass that was required to work and participate in much of society - would not change. The government's message remained the same, vaccines - and now boosters - were the only way out of the pandemic.