Health chiefs are tracking variant that's Omicron and Delta merger

‘Deltacron’ is real after all: Health chiefs are now officially keeping tabs on variant that’s a merger of Omicron and its predecessor Delta

  • In its weekly update the UK Health Security Agency revealed mutant strain in UK
  • Strain evolved in someone who caught both variants at the same time, they said
  • Scientists said  it would not pose ‘too much of a threat’ because of high immunity
  • Health chiefs are now officially keeping tabs on a Covid variant that is a hybrid of the Omicron and Delta strains and has been spotted in the UK.

    The super-mutant Deltacron is thought to have evolved in a British patient who caught both variants at the same time.

    It is not clear how infectious or severe the newly evolved virus is or whether it will impact vaccine performance. 

    A source at the UK Health Security Agency said officials were ‘not concerned’ by the variant because case numbers are ‘low’.   

    Professor Paul Hunter, an infectious disease expert at the University of East Anglia, told MailOnline that it ‘shouldn’t pose too much of a threat’ because the UK has huge levels of immunity against the original Delta and Omicron strains. 

    ‘So at the moment I’m not overly worried at the moment. If both Delta and Omicron are falling then, in theory, this [variant] should struggle to take off.’   

    It comes after reports of a Deltacron case from Cyprus last month were dismissed and put down to sample contamination.

    Experts warned it was likely a case of Omicron and Delta merging would be detected in December, when Omicron infections were surging as it outcompeted Delta. 

    Covid variants can merge — in a process scientifically known as recombination — if they infect the same cell in the same person at the same time, and then swap genes.

    Several ‘recombinant’ variants have been detected in the pandemic, but these have all led to relatively few cases and did not lead to serious outbreaks.

    Scientists say it is ‘rare’ for these to occur, but that when they do the variant is normally ‘less fit’ than its rivals and easily outcompeted. 

    Pictured here are 3D images of the Omicron and Delta viruses. Omicron is nearly five times more mutated than Delta in terms of its spike proteins. While a crossbreeding of the two variants, called a recombination, is a technical possibility, other scientists say recent reports of Deltacron is 'almost certainly' the result of a lab contamination

    Pictured here are 3D images of the Omicron and Delta viruses. Omicron is nearly five times more mutated than Delta in terms of its spike proteins. While a crossbreeding of the two variants, called a recombination, is a technical possibility, other scientists say recent reports of Deltacron is ‘almost certainly’ the result of a lab contamination

    A UKHSA source said: ‘We monitor everything as a matter of course, but we are not particularly anxious about this variant. 

    ‘It is on that list just because we are currently looking at it.’

    They added that it was likely a ‘very safe bet’ that the recombinant strain would not be a problem in the UK.

    UKHSA analysts revealed they had spotted the variant in the agency’s weekly update on variant status in England. 

    But they made no mention of it in today’s technical briefing, which is handed to ministers to update them on the state of the situation in the UK. 


    For a combined variant of the virus to emerge, one person must be infected with two strains of the coronavirus – likely from two separate sources – at the same time, and then the viruses must bump into each other inside the body. 

    Once the viruses are inside the body, the way they spread is by forcing human cells to make more of them. 

    The coronavirus is made up of genetic material called RNA and, to reproduce, it must force the body to read this RNA and make exact copies of it.

    There are inevitably errors when this happens because it happens so fast and so often and natural processes are imperfect. 

    If two viruses are in the same place at once, both being duplicated by the same cells, there is a chance the RNA genes could be mixed up, just as there could be a mix-up if someone dropped two packs of cards at once and picked them all up.

    Most places have dominant variants of the virus so someone getting infected with two is unlikely to begin with. 

    And, for healthy people, there is likely only a window of around two weeks before the body starts to develop immunity and successfully clear out the first version of the virus. 

    This risk window could be cut to days for the majority of people who develop Covid symptoms  – which takes an average of five days – and then stay at home sick.

    But huge, poorly controlled outbreaks like the ones in the UK and US over the winter, significantly raise the risk of the combination events simply because the number of infections is higher. 


    A Delta and Omicron merger variant was reported from Cyprus earlier this month.

    But the announcement was quickly debunked by other scientists, who said the result was likely due to contamination between swabs from different people.

    Moderna’s boss has warned, however, that a recombinant is possible. 

    Professor Hunter told MailOnline: ‘Deltacron doesn’t fill me with dread. 

    ‘The reason is at present that both Delta and most of Omicron — with the exception of BA.2 — are falling quickly and Delta is almost extinct in this country.’

    He added: ‘It will have shared antigens from both Delta and Omicron and we already have high levels of immunity to those.

    ‘So in theory it should not pose too much of a threat. But nobody can predict everything with certainty, so at the moment I am not overly worried.’

    At least three other merger variants have been spotted to date, scientists say, but each fizzled out without causing major outbreaks.

    In one case, a merger between Alpha and B.1.177 was detected in the UK in January last year. But it quickly vanished after leading to just 44 cases.

    In a second one Alpha and a Delta off-shoot (AY.29) merged in Japan in August last year. But this only led to 17 infections before disappearing.

    And in the third incident B.1.634 and B.1.631 merged in the US back in August 2020. This led to 729 infections before vanishing.

    Britain already checks far more of its infections than other countries for variants, making it much more likely the UK will detect a ‘recombinant’ virus.

    Omicron remains the dominant Covid variant in the UK, official data shows, but it is being gradually outcompeted by slightly more transmissible BA.2.

    Scientists expect the virus to gradually evolve into a much more mild but more transmissible version, as it transitions to being endemic.

    But some have warned there is still a risk of a more dangerous variant emerging that is more likely to cause severe disease.

    Professor Francois Balloux, a geneticist at University College London, told MailOnline however that this was unlikely once everyone is vaccinated or had the infection.

    He said: ‘Some variants will be intrinsically more severe than others, but once everyone has been vaccinated and / or infected multiple times, no variant can set us back to levels of covid hospitalisation and death we experienced during the pandemic.’