Two “recombinant” cases have been recorded in the state, according to data from NSW Health’s weekly COVID-19 report.
The virus sequences occur when a case previously carrying two separate virus strains merges, forming a new, single strain that contains genomic regions of both co-infecting strains.
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While no new recombinant infections were identified this week, to date, one Deltacron infection – a mix of Delta and Omicron BA.1 – and one infection of Omicron’s subvariants BA.1 and BA.2 have been identified. It is the first time NSW Health has reported the cases.
At this stage, there is no evidence these strains would be more resistant to vaccines or cause more severe illness.
Genomic sequencing has also detected nine ‘mixed’ infections in the state in recent weeks. This refers to a case where two separate virus sequences are detected at the same time.
The cases include six who contracted both BA.1 and BA.2 at the same time – two of which were detected this week – and three who were concurrently infected with both Delta and Omicron BA.1.
The sub-lineage of the Omicron variant, BA.2, is now the dominant strain of COVID-19 in NSW, making up around 97 per cent of infections sequenced to April 2. The BA.1 sub-lineage is also circulating but at lower levels.
However, the report did note that whole-genome sequencing is prioritized for people admitted to hospital and ICU, and so the proportion of variants identified is “not necessarily reflective of their distribution in the community”.
“This is not a random sample, therefore the proportion of (variants of concern) identified is not necessarily reflective of their distribution in the community,” the report said.
So, what is ‘Deltacrone’?
Recombinants can emerge when a cell is infected with two different strains of a virus at the same time — in this case, the Delta variant and the Omicron variant.
As the viruses invade the cell and replicate, they can, in rare cases, swap parts of their genome and pick up mutations from each other.
Most of the Delta-Omicron hybrid samples found so far feature a genetic code that looks very similar to the original Delta variant, but with one key addition.
“Delta basically grabbed Omicron’s spike protein,” Jeremy Kamil, an associate professor of microbiology and immunology at Louisiana State University Health Shreveport said. “This is essentially Delta trying to hang on by plagiarising from Omicron.”
The World Health Organization has credited extensive genetic sequencing efforts around the world with detecting the hybrid variant and said it would continue to track its spread.
“As we look more, as we do more sequencing, it is possible that this recombinant virus will be detected in other countries, but it is circulating as we understand at very low levels,” Dr Maria Van Kerkhove, the WHO’s technical lead on COVID -19, said.
Recombinants can occur whenever more than one strain of the coronavirus is circulating widely within a population, Kamil said.
For instance, Deltacron likely emerged in places where the Delta and Omicron waves overlapped for a time.
Is it cause for concern?
It’s too soon to know for sure if Deltacron affects humans differently than the Delta variant or the Omicron variant. Because the hybrid’s spike protein comes from Omicron, Kamil said it’s likely that it would behave similarly to that variant.
“That’s not to say it’s not dangerous, because Omicron is dangerous,” he said, “but my strong supposition is that it would match what we see with Omicron.”
Researchers at genetic sequencing company Helix identified a handful of combined Delta-Omicron infections in the US among nearly 30,000 coronavirus samples from late November to mid-February, when both variants were circulating.
Of those samples, researchers identified 20 cases in which people had become infected by both variants at the same time. One of these samples did show some evidence that the variants had exchanged genes, though at low levels.
“There is currently no evidence that the two Delta-Omicron recombinant viruses identified are more transmissible between hosts compared to the circulating Omicron lineages,” the researchers wrote.
– With NBC