Don't panic about 'Deltacron': it might be mixed samples, scientists

Why you DON’T need to panic about ‘Deltacron’: Scientists call for caution over reports of new variant – and say phenomenon is probably just down to sample contamination

  • Deltacron is probably a lab sequencing error rather than crossbreed, experts say
  • Reports of new variant emerged over the weekend from laboratories in Cyprus
  • While Covid crossbreeding can occur previous examples have failed to take-off

‘Deltacron’ probably doesn’t exist, according to scientists who have called for calm over reports of a new Covid hybrid. 

Researchers in Cyprus over the weekend claimed 25 patients had tested positive for a super-variant. 

One academic claimed the samples he’d seen carried a similar genetic structure to Omicron — but also shared quirks seen with the Delta strain. 

Dubbed ‘Deltacron’, news of the potential strain spread rapidly on social media.

But leading virologists have now poured cold water over the findings, insisting it is probably just a result of laboratory contamination. 

They argued fragments of Delta samples may well have been leftover from previous sequencing, leading to the appearance of a new variant. 

Dr Jeffrey Barrett, director of the Covid Genomics Initiative at the Wellcome Sanger Institute, dismissed fears the two strains had merged. ‘This is almost certainly not a biological recombinant of the Delta and Omicron lineages,’ he said. 

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

Cyprus is currently experiencing on of the biggest Covid outbreaks in the world with about double the number of daily new confirmed cases per million people of the UK and US. Source: Our World in Data

People queuing for a Covid vaccine in Cyprus yesterday where the new Deltacron variant was supposedly discovered

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. 

Dr Krutika Kuppalli, an infectious diseases physician who works with the World Health Organization, agreed that it most likely a lab error. 

‘Deltacron is not real and is likely due to sequencing artifact (lab contamination of Omicron sequence fragments in a Delta specimen),’ she said.

‘Let’s not merge of names of infectious diseases and leave it to celebrity couples.’

Dr Thomas Peacock, a virologist from Imperial College London, said the genetical make-up of the ‘Deltacron’ sequences ‘look to be quite clearly contamination’.

But European Molecular Biology Laboratory deputy director general Professor Ewan Birney admitted it was possible, but unlikely, that the variants had merged. 

He said that a ‘key first step’ was to confirm if this recombination has actually occurred or if the sequences are a lab error.

Meanwhile, the Cypriot team who discovered the variant have hit back at reports that their findings are untrue, insisting they have found a new variant.

Dr Leonidos Kostrikis, of the Laboratory of Biotechnology and Molecular Virology in Cyprus ,told Bloomberg that the cases he had found ‘indicate an evolutionary pressure to an ancestral strain to acquire these mutations and not a result of a single recombination event’.

As part of his argument, he claimed that the samples were processed in multiple sequencing procedures in more than one country with at least one from Israel.

‘These findings refute the undocumented statements that Deltacron is a result of a technical error,’ he said. 

While a crossbreeding of Omicron and Delta is technically possible, virologists say it would be incredibly unlikely.

Recombination events, as they are scientifically known, could only occur if someone was infected with two different lineages simultaneously.

If viruses from both strains infected the same cell then they can, in theory, swap their genetic code and make a new version of the virus.

But researchers have said such an event would require very specific conditions and the coincidence of a number of uncontrollable events. 

Dr Krutika Kuppalli an infectious-diseases physician who works with the World Health Organization said people should leave the merging of names to celebrity couples and not viruses

Dr Thomas Peacock a virologist from Imperial College London said ‘The Cypriot ‘Deltacron’ sequences look to be ‘quite clearly’ the result of contamination


A group of mutations — including K417N, S477N, E484A and N501Y — are thought to help Omicron dodge antibodies that usually help fight off the virus.

And N501Y, which was previously seen on Alpha, also helps the virus bind to the body’s cells more easily, allowing for it to enter the body and replicate more efficiently.

Meanwhile, it has 26 mutations on its spike protein that haven’t been seen in previous variants.

Three mutations found on the furin cleavage site may increase Omicron’s transmissibility. These include P681H, which was previously seen in Alpha, as well as H655Y and N679K, which scientists spotted in the Gamma strain.

A series of mutations may help the virus bind to the human cell and help Omicron escape the body’s immune response. These include T478K, which was also on Delta and Q498R, which has not been seen on variants of concerns before.

And missing mutations, including 105-107

Two mutations in the nucleocapsid — R203K and G204R, found on the Alpha and Gamma strains — may be associated with increased infectivity. 

Additionally, there would be no guarantee even if it did occur that it would result in a more dangerous strain.

However, MPs were warned about the prospect of a so-called Deltacron variant just last month.

Covid vaccine maker Moderna’s chief medical officer Dr Paul Burton warned it was ‘certainly possible’.  

Only three strains created by viruses swapping genes have been officially recorded over the course of the pandemic, but these have faded away rapidly.

In one case, Alpha merged with B.1.177 in late January 2021. It only led to 44 cases in the UK before disappearing. 

Instead of recombination, new Covid variants generally emerge on their own. SARS-CoV-2, the virus behind the pandemic, constantly mutates and can pick up genetic quirks as it replicates.  

In most cases the mutations are harmless, but occasionally they can make the virus more transmissible or better able to evade vaccines as is the case with the Omicron variant. 

Omicron has 32 mutations on its spike proteins alone, nearly five times more than Delta.

Claims of the emergence of a new Deltacron variant came a lab in Cyprus which has reportedly submitted its findings to GISAID, an international database that tracks different Covid variants and their spread. 

Cyprus currently has one of the highest Covid cases per head of population rates in the world.  

Stats compiled by Oxford University-backed research team Our World in Data shows that as of yesterday Cyprus recorded 5050 daily Covid cases per million people.

This is nearly double the amount of the UK which recorded 2,607 daily cases per million people on the same date. 

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