How concerning is Omicron offshoot?
Experts say that panic over these detections may be premature, and while there are Omicron variant sub-lineages with growth advantage over their predecessor, this is largely expected and represents a typical evolutionary trajectory.
Recent reports suggest some labs in Delhi have detected a new Omicron family variant, the BA.2.12.1, triggering concerns that it could be linked to the rise in cases being recorded in the Capital.
Experts say that panic over these detections may be premature, and while there are Omicron variant sub-lineages with growth advantage over their predecessor, this is largely expected and represents a typical evolutionary trajectory.
A reason for concern could be if the Sars-CoV-2 takes more surprising strides, like it did when it mutated into the Alpha, Delta and Omicron variants, changing in a way that could make it significantly more transmissible or resistant, or give it an ability to cause more severe illness.
The BA.2.12.1, however, does not fall in this category. Being an Omicron derivative, it has only two additional mutations from its predecessor BA.2 (denoted by the letters S704L and L452Q) in its spike protein. The US CDC believes this variant and another similar Omicron offshoot BA.2.12 (this only has the S704L mutation, not the L452Q), may be contributing to an increasing number of new cases in parts of US.
There are two other Omicron family variants, BA.4 and BA.5, which seem to be causing most new cases in parts of South Africa. These have three changes from the BA.2 variant. The number of changes in all of these sub-lineages is far less when compared to the over 50 changes between Omicron and the ancestral virus seen first in Wuhan.
“This sort of accumulation of mutations that drive further host adaptation and antigenic drift is my general expectation for evolution in the coming months. It’s possible we may have additional ‘Omicron-like’ events, but my baseline is this steady ‘flu-like’ scenario,” said Trevor Bedford, scientist at the Fred Hutch Cancer Research Centre, whose team maintains the virus database Nextstrain, in a tweet on April 19.
A member of the Indian Sars-CoV-2 Genomic Consortium (Insacog) made a similar assessment. “It is an RNA virus that keeps mutating; last year also there were several mutations but our focus was on Delta and the rest were inconsequential in comparison as they did not pose a threat in terms of severity. We will wait and see how this goes,” this person said, asking not to be named.
In other words, there is not enough evidence yet that BA.2.12.1 or the BA.2.12 are significantly worse than the BA.2, which spread widely across India in the months of January and February during the Omicron-fuelled third nationwide wave. In fact, data from virus information repository GISAID analysed by outbreak.info shows that the BA.2.12 was the second most commonly found variant in India at 37% -- during this period, there have been no worrying spikes.
Experts are still watching the situation and are focussing on correctly classifying sequences. “We need to wait for some more time; at least a week or so before anything can be said conclusively. For now, we can say it is largely BA.2 in circulation in the country,” the Insacog member added.
