Explained: What is the "stealth" version of Omicron?

The coronavirus pandemic has plagued the world for the past two years. Even now, the virus shows no evident signs of dissipating as new variants keep developing one after another. Last year, the Delta variant handed over the baton to the rapid-spreading Omicron variant. Although it has just been around for a few months, this strain has already started undergoing mutations. A subvariant has recently emerged, which is being referred to as the “stealth” variant of Omicron, and it has already been detected in almost 40 countries. According to early data, this variant, also known as BA.2, is trickier to detect as compared to the original version. Read on to learn more about what it is. 

What exactly is “stealth” Omicron? 
Essentially, the stealth version of Omicron is a subvariant or a subtype. As already mentioned, scientists have dubbed this version as BA.2. There is also a version which precedes this, known as BA.1. Both of them are considered to be subsets of Omicron. This version contains certain genetic mutations which were not found in the original Omicron lineage. However, it is not clear as of now how significant they are. This is why they have not been categorised as an entirely separate variant, nor does it have a Greek letter name like the others.  

According to the World Health Organisation, some of these mutations are in the spike protein. A part of the data gathered till now indicates that the stealth version could potentially have a higher transmissibility rate than the original version. However, at this point, scientists maintain that it is too soon to make such claims. Moreover, this new subvariant is also harder to detect using PCR tests. In fact, this is the reason why it carries the nickname “stealth” version.  

Why is the BA.2 variant harder to detect? 
Health officials could easily differentiate between the Delta strain and the original Omicron strain using a PCR test as the latter possessed specific genetic features. However, BA.2 is devoid of these features and hence, appears to look similar to Delta. According to scientists, it does not totally mean that it cannot be detected. It simply means that it does not resemble its parent strain, Omicron.  

Which parts of the world has this subvariant been detected in? 
Beginning from mid-November last year, more than 36 countries from all over the world have uploaded close to 15,000 genetic sequences to GISAID which works as a global platform for sharing data related to the coronavirus. Up until now, around 96 of these sequenced cases have come from the United States. However, it has not been reported extensively in the US yet. It has also been detected in Asia and Europe. Specifically in Denmark, this subvariant constituted 45% of all coronavirus cases in the country in January 2022, according to the Danish Statens Serum Institut.