MATT Hancock will make a statement on Covid to the Commons today amid fears a new mutation could delay Boris Johnson's roadmap to freedom.
The Health Secretary will address MPs at 3.30pm over concerns of an Indian variant of the deadly bug.
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Officials are looking into whether the variant could spread more easily and evade vaccines.
And while there's not yet enough data to classify it as a "variant of concern", a reported 160 cases have so far been found in the UK - some of which aren't yet linked to travel.
Public Health England has officially confirmed 73 cases of the B.1.617 variant in England as well as four cases in Scotland.
The variant has two 'escape mutations' - E484Q and L452R – which are causing concern.
India is experiencing a horror surge of Covid. A new curfew will begin in New Delhi tonight after a record 273,810 new infections were reported.
It comes as:
India isn't on the UK's 'red list', meaning those arriving from the country don't have to comply with hotel quarantines.
But Danny Altmann, professor of immunology at Imperial College London, said he expects the country to soon be added to the list.
He told Good Morning Britain: "I am concerned about all the variants.
"I think our roadmap is going well and at the moment, in this country, we are doing rather well, enjoying unlocking - but out there there is the Indian variant, the South African, Brazilian etc, and they do pose a threat."
He said that some people in the population are still vulnerable who can "still be caught out by variants like this".
Prof Altmann added: "At the moment, this particular variant (from India) is called a variant under investigation, not a variant of concern because it hasn't been escalated to that level yet.
"My assumption from everything I've seen is that it will become a variant of concern.
"When it becomes a variant of concern, I'd be quite surprised if India wasn't on the red list."
Meanwhile, Professor Paul Hunter, an epidemiologist at the University of East Anglia, fears the true number of cases in the UK could actually be around 400.
That's because only around a quarter of identified cases undergo tests to identify individual strains.
But another leading expert believes the rise of the Indian variant is unlikely to push lockdown measures back to “square one”.
Professor Adam Finn said: “It will be a gradual erosion.
"It won’t be back to square one. I would be really surprised if that happened.”
And Environment Secretary George Eustice yesterday said there is no evidence the Indian variant is able to "get around" vaccines or is easier to catch.
The PM has vowed to stick with his map for unlocking the UK.
In a speech to the nation earlier this month, the Prime Minister said he believes the UK's lockdown - previously one of the toughest in the world - combined with the dazzling success of the jab's roll-out will get us out of the crisis.
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Under the current roadmap, June 21 is the day life could return almost to normal - although Mr Johnson suggested twice-weekly testing, as well as holiday quarantines and Covid passports, are likely to remain in place for some time to come.
"I want to stress that we see nothing in the present data that makes us think that we will have to deviate from that road map," he said.
"But it is by being cautious, by monitoring the data at every stage and by following the rules - remembering hand, face, space, fresh air - that we hope together to make this road map to freedom irreversible."