The Dutch public health authority said the 13 people were among 61 people who tested positive for the virus on Friday after arriving on the last two flights to Amsterdam’s Schiphol airport before a flight ban was put in place.
All 61 passengers were put into isolation, most at a nearby hotel, while sequencing was carried out.
Dutch Health Minister Hugo de Jonge said he has asked his country’s public health institute for advice on whether additional travel restrictions are needed, but he said he wants to coordinate with his European Union counterparts because he said “I think those are really steps that we will have to take together.”
However a growing raft of restrictions are being imposed by countries around the world as they scramble to slow the variant’s spread, with Israel deciding on Sunday to bar entry to foreign nationals in the toughest move so far.
South Africa was the first country to detect the new omicron variant of Covid-19.
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Two cases have since been confirmed in the UK but South Africa and some other African nations have been added to UK red lists for international travel.
Cases of the Omicron variant have also been confirmed in Germany, Italy, Belgium, Israel, Hong Kong and Australia, just days after it was identified by researchers in South Africa.
However travel restrictions go against the advice of the World Health Organisation, which has warned against any overreaction before the variant has been thoroughly studied.
South Africa’s health minister said travel restrictions on his country are “uncalled for”.
Joe Phaahla claimed international travel restrictions will not prevent the spread of the virus and instead suggested regular testing and mask wearing, including for flying, are effective measures to help live with the virus.
Meanwhile, the doctor who discovered the Omicron variant said the UK is “panicking unnecessarily” when asked on the BBC’s The Andrew Marr Show.
Dr Angelique Coetzee, chair of the South African Medical Association, told the programme she first encountered the variant in a man in his early 30s who presented with tiredness and a mild headache, but none of the usual coronavirus symptoms.
She said: “What we are seeing clinically in South Africa, and remember I’m at the epicentre – that’s where I’m practising – it’s extremely mild. For us, that’s mild cases.”
When asked if the UK was “panicking unnecessarily”, she said: “I think you already have it there in your country and you’re not knowing it, and I would say, yes, at this stage I would say definitely.
“Two weeks from now maybe we will say something different.”