In the last couple of weeks, there has been a noticeable increase in the discovery of BA.2 sub-variant of Omicron from several countries, leading to fresh worries about the possibility of another surge in cases. Last week, the UK Health Security Agency flagged this sub-variant and designated it as a ‘variant under investigation’. And, in its latest weekly bulletin, the World Health Organization noted that a number of countries had reported an increase in the BA.2 sub-variant in the last seven days.
BA.2 is one of the several sub-variants of the Omicron which has spread rapidly across the world since November. The Omicron name was given to the B.1.1.529 lineage after it was designated as a variant of concern. Later, it was found that this lineage had small variations of its own, and the three most common were named B.1.1.529.1, B.1.1.529.2, and B.1.1.529.3. For ease of reference, however, these sub-lineages were later re-classified as BA.1, BA.2 and BA.3.
The Omicron sub-variant that has been most common in circulation till now is BA.1. This continues to be the case even now, though the proportion of BA.2 is on the rise. According to the WHO, 98.8 per cent of all Omicron genetic sequences submitted in global databases till January 25 were that of BA.1 variety. BA.2 retains most of the characteristics of BA.1 but has some more mutations that can give it a distinctive characteristic.
So far, studies have not showed any distinct advantage of BA.2 over BA.1, particularly in the nature of disease that they cause, but the recent rise in BA.2 cases is likely to put a more intense spotlight on this sub-variant.
The increase in proportion of the BA.2 has been noticed mainly in Europe, most prominently in Denmark, where over 8,300 genetic sequences of this Omicron sub-variant have been identified so far. In fact, in Denmark, BA.2 now comprises almost half of all Omicron cases. The United Kingdom has found 607 samples with this sub-variant, while India has discovered 711 till now. The other countries where BA.2 has been found in abundance are the United States, Norway, Sweden and Singapore.
According to the outbreak.info website, that tracks the prevalence of the different lineages of this virus across the world, BA.2 has so far been discovered in 49 countries.
The BA.2 sub-variant is known to be more transmissible than the BA.1 variety, which could possibly explain its surge in recent days. But as of now, researchers have not noticed any difference in the nature of disease that it causes.
Though these are sister lineages, there are important genetic differences between BA.1 and BA.2. In fact, Staten Serum Institute, Denmark’s main institution on infection diseases, said the difference between BA.1 and BA.2 was greater than the difference between the original Wuhan variant which started the epidemic and the Alpha variant, the first major variant that had become dominant in 2020.