Jemma Geoghegan answers some questions about a new variant of Covid-19 emerging overseas 

How widespread is Deltacron and what effect has it had so far?

The virus variant dubbed ‘Deltacron’ has been detected in several countries including UK, France, Denmark and the Netherlands. However, there are several different types of recombinant viruses formed from Delta and Omicron, which I’ll cover later.

What is virus recombination?

When two viruses infect the same individual and the same cell during a co-infection, they can interact and exchange genomic material during replication, generating a virus progeny that has a mixed genome from both of these viruses. This is called virus recombination.

How common is recombination among viruses?

Rates of recombination vary a lot among different types of viruses and it often depends on their genome structure. This coronavirus has been recombining all of the way through the pandemic. However, it has only recently become easier to spot since the viruses circulating are more genetically distinct from one another.

We now have a large number of Omicron cases, mainly the subvariants called BA.1 and BA.2. But when Omicron first took off around the world, there was already very high levels of Delta circulating. This presented a lot of opportunities for different variants to co-infect, recombine and transmit onwards.

What are the new recombinant lineages that have been detected?

The new recombinants that have been talked about recently fall into two categories:

– A mix of Delta and Omicron

– A mix of the subvariants of Omicron (that is, BA.1 and BA.2)

Some of these mixtures, or recombinants, have exchanged only small parts of their genomes while others have swapped lots of genes. For example, ‘XD’ is the new name for the Delta x BA.1 lineage detected in France. It contains the spike protein from BA.1 and the rest of the genome from Delta. The World Health Organization has designated this recombinant a ‘Variant Under Monitoring’.

How concerned should we be about these, and other, recombinants?

There isn’t yet evidence suggesting these recombinant viruses are much more of a public health threat, but recombinants like these should be closely monitored for signs that they might be increasing in number so that we can understand if they induce changes to the virus’ transmissibility, disease severity or ability to escape vaccine-induced immune protection.

Are further recombination events something we should expect and get used to?

Recombinant virus variants are not uncommon and Deltacron is not the first, nor will it be the last, recombinant of this coronavirus.

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