In the drama of the COVID-19 pandemic, the delta variant of the coronavirus has stood out, recently dethroned by omicron, which has become dominant in a short time in most countries of the world. However, it seems that the thing does not end there, since a new secondary has entered the scene, it is BA.2, a sublineage of omicron that has already been called the stealthy subvariant.
And it is that several surnames have been attributed to the original ómicron variant: BA.1, BA.2 and BA.3. The second is the one that has set off the alarms of microbiologists and epidemiologists, since more and more cases are occurring, and specifically, according to the latest WHO epidemiological update as of February 1, 2022, there are already 57 countries that have registered this sub-variant among their citizens, including Spain.
Many media outlets refer to BA.2 as the stealthy variant, and it is not by chance, as this mutation has resulted in a new genome capable of escaping some of the traditional mutation detection methods, so it could even There are many more cases than are currently known. However, this is not exact, “it’s not that the test doesn’t pick it up, it’s just that it doesn’t look like omicron,” and it can be confused with delta, says US infectious disease expert Dr. Daniel Kuritzkes. “Don’t be under the impression that ‘stealth micron’ means we can’t detect it. All of our PCR tests can still detect it.”
What is the origin of the BA.2 subvariant and in which countries has it been detected?
The first time this omicron sublineage was detected was in China several weeks ago, when they were reconstructing the genetic sequencing of a group of COVID-19 patient samples. Other experts believe that this sub-variant could have its origin in India, but very little is still known about it.
The United Kingdom Health Security Agency (UKHSA) has already reported that it is closely monitoring this new subvariant and that, although the number of cases is still low, further analysis will be carried out to learn as much as possible about this new sublineage. As of January 21, “there have been 426 cases of BA.2 omicron confirmed by whole genome sequencing (WGS), the first dated December 6, 2021. The areas with the highest number of confirmed cases are London (146) and the southeast (97)”, they explained in the statement.
Since November 17, 2021, 57 countries have reported cases of the BA.2 subvariant in their territories, the first from the Philippines, although the majority come from Denmark, where this stealthy variant already accounts for 45% of new infections in recent years. 10 days. India, Singapore, Australia, Israel, Germany, Canada or Sweden are also on the list of countries where this omicron sublineage has already been detected, being for now more prevalent in Asia and Europe. In Spain at the moment only one case has been reported on January 26.
Is the BA.2 subvariant of omicron more dangerous? What differences does it present?
This new subvariant is characterized by the large number of mutations it has with respect to the original. As explained by the UKHSA, ómicron BA.2 lacks the genetic deletion in the spike protein that causes S gene target failure (SGTF) in some PCR tests, hence it can slip through and result in a false negative.
To understand how this subvariant has developed, it is necessary to know that when the infection occurs, the virus multiplies in human cells and copies its genetic sequence. However, during this process copy errors can occur, which is what is called mutations, and from there new variants and subvariants emerge.
The virologist Tom Peacock He told on his Twitter that “the constant growth in several countries is evidence that BA.2 may be a little more transmissible than BA.1. Unfortunately, we currently don’t have a solid control over antigenicity, severity, or much evidence of how much more transmissibility BA.2 might have over BA.1.”
However, the expert believes that some conclusions can be drawn, albeit somewhat hasty, and that they should be taken with a grain of salt. These would be that there does not seem to be an important difference in the cases of both subvariants, since they seem to generate the same symptoms and without notable changes in severity.
In fact, it appears that the two versions of omicron have so much in common that infection with the original mutant may “provide cross-protection against BA.2,” says Dr. Daniel Kuritzkes, an infectious disease expert at Brigham and Women’s Hospital. .
According to a study by the Technical University of Denmark, still in preprint, the BA.2 subvariant is more contagious than the original BA.1. However, it has also found that people who are vaccinated against COVID-19 have a lower risk of transmitting the infection if they get BA.2. Specifically, it is estimated that the probability of contagion is 39% higher with BA.2, while with BA.1 the risk is 29%.
For her part, Dr. Meera Chand, director of incidents of COVID-19 at UKHSA, has stated that “the nature of viruses is to evolve and mutate, so it is to be expected that we will continue to see new variants emerge as it progresses. the pandemic. Our ongoing genomic surveillance allows us to detect them and assess whether they are significant. So far, there is insufficient evidence to determine whether BA.2 causes more severe disease than omicron BA.1, but data is limited and UKHSA is continuing to investigate.”
Do vaccines protect against COVID-19 from the BA.2 subvariant of ómicron?
According to virologist Tom Peacock, this new sublineage should not call into question the effectiveness of existing COVID-19 vaccines. “There are likely to be minimal differences in vaccine effectiveness against BA.1 and BA.2. Personally, I’m not sure BA.2 is going to have a substantial impact on the current wave of the omicron pandemic,” the expert tweeted.
But it must be emphasized that there is still not enough scientific evidence in this regard on this very recent sublineage. Therefore, they recommend not to be alarmed and wait to see what is known about BA.2. “We don’t have hard data yet, we can make some educated guesses that may turn out to be correct, but the next few weeks should make things much clearer,” concludes Peacock.
For its part, the World Health Organization (WHO) has recommended that scientists focus their attention on investigating the BA.2 version of the omicron variant, which is spreading rapidly around the world and whose impact it could have is unknown. have in the evolution of the COVID-19 pandemic.
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