Health experts are investigating a new 'Thai variant' of the coronavirus which has been connected to more than 100 cases in the UK.
The variant, known as VUI-21MAY-02 (C.36.3), was first detected in Thailand in people who had travelled from Egypt, Public Health England (PHE) has confirmed.
There have now been 109 cases detected in the UK, PHE said in an update.
It has now been designated a 'variant under investigation' and PHE is carrying out laboratory testing to better understand the impact of the mutations on the behaviour of the virus and determine whether it reaches the threshold of being a 'variant of concern'.
An update on the government website said: "There is currently no evidence that this variant causes more severe disease or renders the vaccines currently deployed any less effective."
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It added: "PHE is carrying out laboratory testing to better understand the impact of the mutations on the behaviour of the virus.
"All appropriate public health interventions will be undertaken, including additional contact tracing and targeted testing.
"Where cases have been identified, additional follow-up of cases, testing of contacts and if required targeted case finding will limit its spread."
The news comes as Matt Hancock confirmed that cases of the Indian variant of COVID-19 have doubled in a week to reach almost 7,000, although hospital admissions remain broadly flat, data shows.
The health secretary told a Downing Street press conference on Thursday that up to three-quarters of new coronavirus cases were the Indian variant, though he stressed that vaccines were helping keeping people out of hospital.
Data from Public Health England (PHE) for up to 26 May showed 6,959 cases of the Indian variant of coronavirus had been confirmed in the UK – a rise of 3,535 on the previous week.
The local areas most affected by variant continue to be Bolton, Bedford and Blackburn with Darwen, while seven further areas in England have more than 100 confirmed cases: Leicester, Sefton, Nottingham, Wigan, Central Bedfordshire, Manchester and Hillingdon.
Professor Neil Ferguson, from Imperial College London, whose modelling was instrumental to the UK locking down in March 2020, said the Indian variant was now "the dominant strain" in the UK and the full reopening of society on June 21 "hangs in the balance".
Professor Danny Altmann, of Imperial College London, also told Sky News that the final stage of the roadmap, which would see all limits on social contact lifted, were "balanced on a knife edge".
He said: "Frankly, it's alarming isn't it? Because what we've essentially done is set back our clock… going back to the kind of figures we were last seeing about a month ago in terms of new cases. So I think it's troubling."
Asked in the Commons by former health secretary Jeremy Hunt what measures could be taken to ensure June 21 could go ahead, Hancock said it was too early now to say.
He told MPs: "We will make a formal assessment ahead of June 14 as to what step we can take on the 21st, and in that we will be both driven by the data, we will be advised on and guided by the science, and we will be fully transparent both with this House and with the public in those decisions.”
Later, Boris Johnson told reporters he didn't "see anything currently in the data" to divert from the 21 June target, adding: "But we may need to wait. Don’t forget the important point about the intervals between the steps of the road map – we put that five weeks between those steps to give us time to see what effect the unlockings are having."
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