Cases of the SARS-CoV-2 variant Omicron have escalated globally over the past two months, with many countries experiencing peaks higher than previous variants.

Now we’re seeing cases of a sub-variant of Omicron, known as BA.2, emerge.

Rather than a daughter of the Omicron variant BA.1 (or B.1.1.529), it’s more helpful to think of BA.2 as Omicron’s sister.

Remind me, what is a variant?

Viruses, and particularly RNA viruses such as SARS-CoV-2, make lots of mistakes when they reproduce. They can’t correct these mistakes, so they have a relatively high rate of errors, or mutations, and are constantly evolving.

When the genetic code of a virus changes as a result of these mutations, it’s referred to as a variant.

Omicron is a “highly divergent” variant, having accumulated more than 30 mutations in the spike protein. This has reduced the protection of antibodies from both prior infection and vaccination, and increased transmissibility.

When do health authorities worry about a new variant?

If changes in the genetic code are thought to have the potential to impact properties of the virus that make it more harmful, and there’s significant transmission in multiple countries, it will be deemed a “variant of interest”.

If a variant of interest is then shown to be more infectious, evade protection from vaccination or previous infection, and/or impact the performance of tests or treatments, it is labelled a “variant of concern”.

The World Health Organization (WHO) classified Omicron a variant of concern on November 26 because of its potential to cause higher reinfection rates, increased transmissibility and reduced vaccine protection.

Full story at The Conversation: https://theconversation.com/ba-2-is-like-omicrons-sister-heres-what-we-know-about-it-so-far-176137

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