XE, XD & XF: what to know about the Omicron hybrid variants.

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Authors: Greg Basky and Lauren Vogel
Date: May 9, 2022
From: CMAJ: Canadian Medical Association Journal(Vol. 194, Issue 18)
Publisher: CMA Impact Inc.
Document Type: Article
Length: 918 words
Lexile Measure: 1480L

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Canada recently reported its first cases of the Omicron subvariant XE, one of several hybrid variants of SARS-CoV-2 that have emerged since the beginning of this year.

First detected in the United Kingdom in January, XE has genetic material from the Omicron subvariants BA.1 and BA.2, along with three new mutations that are not present in either pre-existing strain.

Hybrid versus mutant

Hybrid or "recombinant" subvariants like XE occur when two different strains of a virus infect the same cell at the same time and blend their genetic material to produce a new variant.

Compared with the slower process of a virus mutating through errors in the replication of its genetic code, recombination can allow for major, rapid changes in transmissibility, severity, and resistance to vaccines and treatments.

According to Susan Hopkins of the UK Health Security Agency, "Recombinant variants are not an unusual occurrence, particularly when there are several variants in circulation, and several have been identified over the course of the pandemic to date."

Like variants that occur via mutation, most hybrid strains die off relatively quickly, and some may not differ noticeably from their parent variants.

At least two recombinant subvariants in which Delta and Omicron lineages combine --XD and XF--have emerged in Europe in recent months. So far, there is no evidence to suggest that these so-called "Deltacron" strains are more transmissible or cause worse...

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Gale Document Number: GALE|A703277333