The Omicron variants: An overview of the tracking and the related research

Omicron splinters into fast-spreading lineages, highlighting coronavirus's evolution A burgeoning form of Omicron, called BA.2.12.1 — itself a sublineage of the BA.2 branch — now accounts for nearly one in five cases of Covid-19 in the U.S. Andrew Joseph STAT

Scientists around the world are discovering and tracking newer forms of the Omicron coronavirus variant, showing how even when a strain becomes globally dominant, it continues to evolve and can splinter into different lineages.

Case in point: Updated data released Tuesday showed that a burgeoning form of Omicron, called BA.2.12.1 —  itself a sublineage of the BA.2 branch of Omicron — now accounts for nearly one in five infections in the United States. It’s eating into the prevalence of the ancestral BA.2, highlighting the emergent virus’s transmission advantage over its parent. BA.2 now accounts for about 74% of cases, while the remaining 6% or so are from the BA.1 branch of Omicron, the first form of the variant that took over globally and whose prevalence has been falling as BA.2 became dominant.

The menagerie can be dizzying to track, especially because all these cases technically fall under the Omicron umbrella. But even as scientists closely monitor the divergence of Omicron, early signs suggest the different lineages don’t substantially differ in terms of how virulent they are or in their ability to evade the protection generated by immunizations. While some of the newer forms of the virus might be better spreaders than others, their emergence doesn’t necessarily result in huge increases in cases.

Already, the growth of BA.2 was helping drive up cases in parts of the United States, particularly in the Northeast. As BA.2.12.1 snowballs, it could give the virus an extra transmission boost. Last week, New York state officials noted that the sublineage was contributing to comparatively high infection rates in certain parts of the state and estimated that it had a 25% growth advantage over BA.2.  ...