- Coronavirus pandemic
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The UK cannot take a risk over a new coronavirus variant circulating in southern Africa which may be able to evade the protection of vaccines, the transport secretary has said.
Grant Shapps told the BBC the UK "acted immediately" with a "safety first" approach by placing six countries on its red list to restrict travel.
Susan Hopkins, the UK Health Security Agency's chief medical adviser, said it was the "most worrying" variant yet.
No cases have been confirmed in the UK.
From midday travellers from South Africa, Namibia, Zimbabwe, Botswana, Lesotho and Eswatini will have to self-isolate for 10 days, with those arriving after 04:00 GMT on Sunday required to quarantine in a hotel.
All flights from the six countries are also being suspended until the hotel quarantine system is in operation.
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South Africa, Hong Kong and Botswana have identified just 59 cases of the variant, known as B.1.1.529, so far, while Israeli media also reports one case has been identified from a traveller.
Mr Shapps paid tribute to South Africa's fast and transparent response, and said of the UK's decision to restrict travel: "This is a safety-first approach."
He said the UK "acted immediately" because "we can't take risks when it comes to something that could defeat the vaccine", as scientists fear may be possible.
People who have returned from the six countries in Africa in the last 10 days will be contacted and asked to take a PCR test, but Mr Shapps said, with only a small number of cases identified worldwide, they do not expect to detect any in the UK.
"We know from lots of experience now that you can never stop these things but early action buys you more time," Mr Shapps said.
Health Secretary Sajid Javid is due to update the House of Commons about the Covid situation at 11:00 GMT.
Scientists say the variant has 50 mutations overall and more than 30 on the spike protein, which is the target of most vaccines and the key the virus uses to unlock the doorway into our body's cells.
Prof James Naismith, director of the Rosalind Franklin Institute at Oxford University, said: "It's bad news, but it's not doomsday."
The variant would "almost certainly" make vaccines less effective, but they would still work to some extent. New drugs to treat Covid-19 would not be affected by the variant, he suggested.
One scientist told me this was the worst variant they'd seen – look at it on paper and it's not hard to see why.
It is the most heavily mutated variant so far and is now radically different to the form that emerged in Wuhan, China.
That means vaccines, which were designed using the original, may not be as effective.
And some of its mutations are known to increase the ability of coronaviruses to spread.
But there have been many variants that looked bad on paper before, but haven't taken off.
There are early signs this virus is spreading in South Africa and may already be in every province in the country.
But the big questions – how much does it evade vaccines, is it more severe, does it spread faster that Delta – are unanswerable for now.
- Read more from James.
It had not been proven that the variant was more transmissible, but it has mutations consistent with the Delta variant and appeared to spread more quickly than other variants, Prof Naismith told BBC Radio 4's Today programme.
"The travel ban will slow it down," he said. "It will get here but it will give us a few more weeks."
Dr Hopkins said scientists needed to learn more about the variant before they could be certain but it appeared that "there's mutations which increase infectivity, mutations that evade the immune response – both from vaccines and from natural immunity – and mutations that cause increased transmissibility".
She said South Africa had a very low rate of cases which more than doubled in two weeks. On average, each infected person in Gauteng, where the variant was first seen, is passing the virus on to two people, a rate of transmission not seen since the beginning of the pandemic, she said
But she added the variant, which was first reported on 22 November, could be detected easily with genomic sequencing and it was "reassuring" it had not been seen in the UK yet.
From midday non-UK and Irish residents will be banned from entering England if they have been in the six countries in the past 10 days.
Any British or Irish resident arriving from the countries after 04:00 GMT on Sunday will have to quarantine in a hotel, with those returning before that being asked to isolate at home.
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Germany, Italy, Israel and Singapore are among the countries that have also implemented travel restrictions on southern African countries after the emergence of the variant, while the European Commission has said it will propose to halt air travel from the region across the EU.
But African experts questioned the effectiveness of the measures. Dr John Nkengasong from the Africa Centres for Disease Control said imposing travel restrictions "has never helped reduce the spread of any variant across the world".
The announcements prompted a slump in airline shares, with the share price of British Airways' owner IAG dropping by 15%.
Travel expert Simon Calder told BBC Breakfast it was a "disaster" for the aviation industry as it tried to recover.
At Cape Town airport, one woman whose sister had just made it on to a flight back to the UK said: "It's absolutely ridiculous they've imposed it again so quickly without really investigating this new variant.
"We're just trying to get on our feet again with tourism and this will just kill it."
But another traveller was unconcerned. "I love being back in Cape Town, so if I get stuck here – what a pleasure!"
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