For the most up-to-date information on the global trends of COVID-19 variants and mutations, check Cornelius Roemer's monthly SARS-CoV-2 Variant Reports on GitHub.
XBB descendants continue growing across the globe. In sequences collected at the beginning of April, less than 15% were non-XBB*, about half the proportion a month earlier (30% beginning of March).
At the start of April, there was particularly little non-XBB* left in the USA (<5%). China had the highest proportion of non-XBB* (~75%) though XBB* is quickly making inroads there as well. Japan and South Korea also still have sizeable non-XBB* proportions.
Spike mutation S:486P is now present in the vast majority of XBB*: less than 5% of XBB* do not have 486P.
The major XBB* sublineages are currently:
XBB.1.16* has grown to dominance in India and is increasing globally. The extra advantage over XBB.1.5*-like lineages appears to be mutation S:478R (in addition to 486P). As seen with 486P, 478R has arisen multiple times within XBB and appears to predictably confer a growth advantage in the lineages that acquire it (the more beneficial a mutation, the more often it arises independently, recall 346T in BA.5).
While XBB.1.16* is currently the most prominent XBB lineage with both 486P and 478R, other such lineages could in the mid-term replace it.
India, where XBB.1.16* has been dominant since end of February, has seen a steep rise in confirmed cases which have grown by a factor of 100 since the start of February. It is difficult to say to which extent this wave is driven by XBB.1.16* and to which extent it is a seasonal effect: a strikingly similar pattern (40-fold growth from beginning of February to end of April) was seen at exactly the same time of year in 2021. Back then, the wave coincided with the emergence of Delta. So the answer is possibly both effects matter: emergence of new variant and seasonal effects.
A comprehensive discussion of XBB.1.16, including clinical properties, can be found in the recent WHO Risk Assessment from April 17.
In addition to 486P and 478R, a number of other Spike mutations have been observed repeatedly in XBB*. While some, like 456L, did not initially appear to confer a significant growth advantage, growth (dis)advantages conferred by mutations can change over time, as population immunity builds against a variant. Recently, 456L has started to appear independently and grow in frequency. What is currently only a slight growth advantage (~20% per week) could grow in the future.
Besides 456L, mutations 403K and 521S have been observed to increase in share and are part of a number of lineages. This list is not exhaustive.
In particular for vaccine variant selection, it is important to keep an eye on remaining non-XBB diversity (~15%): the fewer non-XBB there are, the more obvious and less risky a switch to XBB (or sublineage thereof) is.
The non-XBB diversity can be broken down roughly into (share is always with collection date beginning of April):
While the future is most likely to look like XBB*, it is possible that BA.2.75* may play a role (potentially through recombination with XBB, like recently designated XCC). There is a small but non-zero chance, that a more divergent lineage may emerge from XBC, XAY or BA.2.3.20
Most of the hundreds of sub-variants that have descended from Omicron have not picked up traction to spread globally. However, certain mutations can increase the risk of a variant spreading globally. Below are sub-variants that have been identified as concerning for global spread.
| PANGO Lineage | Lineage or Alias | Concerns |
|---|---|---|
| XBF | BA.5.2 & CJ.1 (BA.5 & BA.2) | BA.2 & BA.5 recombinant |
| DS.1 | BN.1.3 (BA.2) | Most immune evasive + High ACE-binding affinity |
| XBL | XBB.1 & BA.2.75 | XBB/BA.2.75 recombinant |
| DN.1.1.1 | BQ.1 (BA.5) | Exceptional ACE-binding affinity |
| XBB.1.5.13 | XBB.1.5 | |
| DV.1 | CH.1.1.1 (BA.2.75) | |
| EG.1 | XBB.1.9.2.1 | |
| EK.2 | XBB.1.5.13.2 | Even better ACE2 binding without losing immune escape than XBB.1.5 |
| EL.1 | XBB.1.5.14.1 | |
| EM.1 | XBB.1.5.7.1 | Growth advantage |
| XBC.1.6 | XBC.1* |
Last Updated: February 28, 2023
Red Box = Zone of Concern (high immune escape and high ACE2 binding affinity)
