Here's what we know so far about Ba.2, the "brother" of the Omicron

The World Health Organization now defines it as a species under investigation. This is not the first version to have sub-dynasties. At the end of last year, Delta "Plus" or AY.4.2 was widely reported and then came Omicron

Paul Griffin, Associate Professor, Infectious Diseases and Microbiology, University of Queensland

The omicron variant of the SARS-CoV-2 coronavirus has spread rapidly around the world over the past two months, with many countries experiencing higher peaks than in the peak waves of previous variants.

Cases of a sub-variant of Omicron, known as BA.2, have also now been discovered. Instead of a descendant version of the Omicron, it is better to think of BA.2 as the "brother" of the Omicron.

Remind me, what is a variant?

Viruses, and especially RNA viruses such as SARS-CoV-2, accumulate many mistakes as they reproduce. They cannot correct these mistakes, so they have a relatively high rate of mistakes, or mutations, and are constantly evolving. When the genetic code of a virus changes significantly as a result of these mutations, it is called a variant.

Omicron is a "very different" variant, having accumulated more than thirty mutations in the spike protein. The changes caused by the mutations reduced the protection provided by antibodies created from a vaccine or previous infection, and its infectivity is also much greater.

When health authorities are concerned about a new version?

If it is thought that changes in the genetic code have the potential to affect the properties of the virus that make it more harmful, and there is a significant spread of it in several countries, it will be considered a "variant of interest".

If it is later proven that such a variant is more contagious, evades protection against vaccination or previous infection and/or affects the performance of tests or treatments, it is marked as a "worrying variant".

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

What is a dynasty? Omicron?

A lineage, or subvariant, is a genetically related group of virus variants that originate from a common ancestor. The Omicron version includes three sub-lineages: B.1.1.529 or BA.1, BA.2 and BA.3.

The World Health Organization now defines it as a species under investigation. This is not the first version to have sub-dynasties. At the end of last year, Delta "Plus" or AY.4.2 was widely reported and then came Omicron.

What is different in-BA.2?

While the first BA.2 sequences were discovered in the Philippines and now thousands of cases have been discovered around the world, including in the United States, Great Britain and some in Australia - its origin is still unknown.

The exact characteristics of BA.2 are also still being investigated. While there is no evidence so far that it causes more serious disease, scientists have some specific concerns.

1. It's harder to tell the difference

A marker that helped distinguish Omicron (BA.1) from other variants of SARS-CoV-2 in PCR tests is the absence Garden S , known as "S gene target failure". But this marker is not relevant for BA.2. The inability to identify this lineage in this way has led some to label it a "creeping sub-variant".

But that doesn't mean we can't diagnose BA.2 with PCR tests. It just means that when someone tests positive for SARS-CoV-2, it will take us a little longer to know which variant is responsible, using genome sequencing. This was the case with previous versions.

2. It may be more contagious

Perhaps most concerning is the emerging evidence that BA.2 may be more infectious than the original omicron, BA.1.

study First from Denmark , in which BA.2 has largely replaced BA.1, suggests that BA.2 increases the susceptibility of unvaccinated individuals to infection by slightly more than twofold compared to BA.1.

The researchers estimate that even fully vaccinated people are 2 times more sensitive to BA.2.5 than BA.1, and those vaccinated with only three shots are almost three times more sensitive. The study examined more than 2,000 primary cases of BA.2 to determine the number of cases that occurred during a seven-day follow-up period.

The researchers also estimated the secondary attack rate (essentially, the probability of infection occurring) at 29% for households infected with BA.1 compared to 39% for those infected with BA.2.

This Danish study is still in preprint, meaning it has not yet been tested by independent scientists, so more research is needed to confirm whether BA.2 is truly more contagious than BA.1.

It is likely that we will see new versions

We should expect that new variants, sub-variants and lineages will continue to appear. With such high levels of infection, the virus has many opportunities to reproduce and errors and mutations continued to appear.

The way to address this, of course, is to try to slow down the infection and reduce the pool of susceptible hosts where the virus can replicate freely. Strategies such as social distancing and wearing masks, as well as increasing vaccination rates worldwide, will slow the emergence of new variants and lineages.

For an article in The Conversation

More of the topic in Hayadan:

• Is Omicron more contagious than Delta? A virus evolution expert explains what researchers know and don't know
• Do new versions of the corona such as Omicron appear because of low vaccine coverage?
• Are the booster vaccines for corona effective against the Omicron strain? Everything you need to know
• The omicron species - what do we know?