The World Health Organization now defines it as a strain that is being tested. This is not the first version to have sub-dynasties. Late last year, Delta “Plus” or AY.4.2 was extensively reported and then came Omicron
Paul Griffin, Associate Professor, Infectious Diseases and Microbiology, University of Queensland
The Omaricon variant of the Corona SARS-CoV-2 virus has spread rapidly around the world over the past two months, with many countries experiencing higher peaks than the wave peaks of previous versions.
Cases of a sub-variant of Omicron, also known as BA.2, have now also been discovered. Instead of a descendant version of the Omicron it is worth thinking more about BA.2 as the “brother” of Omicron.
Remind me, what is a variant?
Viruses, and especially RNA viruses such as SARS-CoV-2, accumulate a lot of errors as they multiply. They cannot correct these errors, so they have a relatively high rate of errors, or mutations, and they 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 have reduced the protection afforded by antibodies created by a vaccine or previous infection, and its ability to infect is much greater.
When are health authorities concerned about a new version?
If changes in the genetic code are thought to have the potential to affect the properties of the virus that make it more harmful, and there is a significant spread of it in a number of countries, it will be considered an “interesting variant”.
If it is subsequently proven that such a variant is more contagious, evades protection against previous vaccination or infection and / or affects the performance of the tests or treatments, it is marked as a “worrying variant”.
The World Health Organization (WHO) classified Omicron as a cause for concern on November 26 because of its potential to cause higher recurrence rates, increased transmission and reduced vaccine protection.
What is a lineage? Omicron?
A lineage, or sub-variant, is a genetically related group of virus variants that originate in 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 strain that is being tested. This is not the first version to have sub-dynasties. Late last year, Delta “Plus” or AY.4.2 was extensively reported and then came Omicron.
What is different in-BA.2?
While the first sequences of BA.2 have been discovered in the Philippines and now thousands of cases have also been discovered around the world, including in the United States, the United Kingdom and some in Australia – its origin is still unknown.
Even the exact properties of BA.2 are still being investigated. While there is so far no evidence that it causes a more serious illness, scientists have some specific concerns.
1. It’s harder to differentiate
A marker that helped differentiate Omicron (BA.1) from other versions of SARS-CoV-2 in PCR testing is the absence of the S gene, known as the “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 as a “sneaky sub-variant.”
But that does not mean we can not 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 version is responsible, using a genome sequence. This has been the case with previous versions.
2. It may be more contagious
Perhaps the most worrying thing is the emerging evidence that BA.2 may be more contagious than the original omicron, BA.1.
A preliminary study from Denmark, in which BA.2 largely replaced BA.1, suggests that BA.2 increases the susceptibility of unvaccinated people to infection by a little more than twice as much as BA.1.
The researchers estimate that even fully vaccinated individuals are 2.5 times more sensitive to BA.2 than to BA.1, and those vaccinated with only three injections are almost three times more sensitive. The study examined more than 2,000 initial 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 rate of attacks (actually, 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 early print, meaning it has not yet been tested by independent scientists, so further research is needed to confirm whether BA.2 is indeed more contagious than BA.1.
New versions are likely to be seen
We should expect new versions, sub-variants and lineages to 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 treat 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 mask wearing, as well as increasing vaccination rates around the world, will slow down the emergence of new versions and lineages.
For an article in The Conversation
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