After Omicron, Delta recombinants variant, World Health Organisation (WHO) has now warned of the 2nd COVID mutant strain XE (hybrid strain of 2 Omicron subvariants) stating that early studies indicate that its growth rate advantage is ~10% as compared to BA.2. So far, three hybrid or recombinant viruses have been detected – XD, XE, XF – (two are combination of Delta and Omicron and the third is the hybrid strain of 2 Omicron subvariants).
What are the 3 newly identified recombinant strains?
A UK Health Security Agency (UKHSA) study recently revealed that currently as many are 3 hybrid COVID variants are circulating. The two different combinations of Delta and BA.1 are XD and XF. The third is XE.
XD is the new name for the French Delta x BA.1 lineage. It contains the Spike protein of BA.1 and the rest of the genome from Delta. It currently comprises several 10s of sequences.
XF is a UK Delta x BA.1 lineage. It has the Spike and structural proteins from BA.1 but the 5′ part of its genome from Delta. It comprises several tens of sequences currently.
XE is a large UK BA.1 x BA.2 lineage. It has the Spike and structural proteins from BA.2 but the 5′ part of its genome from BA.1. It comprises several hundred sequences at present.
After Omicron, Delta recombinant, WHO warns of XE…
The World Health Organization issued a report yesterday with some preliminary findings about XE, reports said.
“The XE recombinant was first detected in the United Kingdom on 19 January and >600 sequences have been reported and confirmed since,” reads the WHO document. “Early-day estimates indicate a community growth rate advantage of ~10% as compared to BA.2, however this finding requires further confirmation.”
Earlier, the UN health agency had issued a warning against Omicron, Delta recombinant virus saying that with both Omicron and Delta circulating in a massive scale, this was highly expected.
Of XD, XE and XF, which is most severe?
Eminent virologist Tom Peacock explained that recombinants that contain the spike and structural proteins from a single virus (like XE or XF) are fairly likely to act similarly to thier parental virus.
XD is maybe a little more concerning. It has been found in Germany, Netherlands and Denmark and it contains the structural proteins from Delta – if any of these recombinants were to act much differently than its parent it might be XD.
All these recombinants (including the smaller clusters that have not been assigned) should clearly be closely monitored for signs of growth and attempts should be made to isolate and characterise where possible, he said in a series of tweets.