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"Dual Infections" Of Delta & Omicron: What's The Risk?


Tom Hale

Tom is a writer in London with a Master's degree in Journalism whose editorial work covers anything from health and the environment to technology and archaeology.

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Transmission electron micrograph of SARS-CoV-2 virus particles (gold) within endosomes of a heavily infected nasal Olfactory Epithelial Cell. NIAID/Flickr (CC BY 2.0)

The Omicron variant is currently tearing through many parts of the world and could soon “outpace” previously known variants, such as the especially deadly Delta variant. With all of these variants still in circulation, some have raised concerns of “dual infections” where people are simultaneously infected with both Delta and Omicron, potentially creating the conditions for the emergence of a new hybrid "super-mutant" variant.

But are these concerns valid? Speaking to IFLScience, one expert explains that it is possible that a dual infection could create a hybrid variant – after all, it's happened before with SARS-CoV-2 – but it's "highly unlikely" to result in a more dangerous virus. 


The concern was first flagged up by the chief medical officer of Moderna, Dr Paul Burton, while speaking to members of parliament on the UK’s Science and Technology Committee on December 14. While noting the high numbers of Delta and Omicron cases in the UK, Dr Burton said there’s evidence from South Africa, where Omicron was first identified, in which immunocompromised people have been found to harbor both variants. 

“That would be possible here [in the UK], particularly given the number of infections that we were seeing,” Dr Burton remarked.

“It certainly gives the opportunity for the two viruses to, what we call, ‘recombinate.’ They can now begin to share genes and swap genes over.”

Genetic recombination is the trade of genetic material between viruses (or even more complex organisms). In theory, if a person is co-infected with both variants, the viruses could infect the same cell, providing them with an ideal opportunity to mingle and mix-and-match genetic material. This could potentially result in a hybrid strain that's composed of genetic material from both variants. 


This threat, however, remains purely hypothetical for now, but it’s something that Dr Burton believes should be taken into consideration.

“So, the biology of Omicron and the situation we're in, given the Delta pressure right now, is really important to think about,” he said.

There's some evidence that SARS-CoV-2, the virus that causes COVID-19, has previously undergone recombination. In February 2021, New Scientist reported that one team of scientists found evidence that the Alpha variant had shared genetic material with the lesser-known Epsilon variant to produce a hybrid "mash-up" variant. However, little came of this recombination and the hybrid variant did not go on to become a "super-mutant" variant hell-bent on world domination. 

"There have been previous reports of co-infection with two different or multiple SARS-CoV-2 lineages but this has been a relatively rare event. Often one lineage will out-compete the other e.g. alpha co-infections with delta changed to the single infection with the dominant delta variant," Professor Lawrence Young, virologist and Professor of Molecular Oncology at Warwick Medical School, University of Warwick, told IFLScience. "There is no clear evidence that co-infection influences disease symptoms or treatment response." 


So, while the threat of dual infections and hybrid variants may sound scary, the threat is currently nothing to lose sleep about yet.  

"Community transmission of recombinant SARS-CoV-2 viruses has previously been detected, including in the UK. With high levels of both delta and omicron infection it is possible that a recombination event could occur in a dually infected individual. But to be selected and spread, this recombination would have to increase the fitness of the virus to infect and replicate," Professor Young added.

"Given the increased transmissibility of the omicron variant and the number of mutations in it spike protein and other regions, it is highly unlikely that any recombination event would result in a more dangerous virus."


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