All circulating variants currently reported belong to the Omicron family. But the virus has continued evolving and accumulating mutations, particularly in the receptor binding domain of the Spike protein. The result is the simultaneous rise of multiple descendants of Omicron BA.2 and BA.4/5, sharing common mutations that allow the virus to better escape recognition by neutralizing antibodies (a process called convergent evolution).
January 2023: One of these sublineages is XBB1.5, derived from XBB1, a recombinant between two Omicron BA.2 subvariants. It has mutations in Spike that allow it to better escape antibody recognition (as XBB1 and many other Omicron subvariants), but has one additional mutation (S486P) that helps it bind better to the human ACE2 receptor. This gives it a growth advantage over other currently circulating Omicron subvariants. There is no evidence for the moment that XBB1.5 causes more severe infections, and current vaccines remain effective.
March 2023: Another subvariant currently under observation is XBB1.16. It has been identified in many countries, where it is replacing the other subvariants in circulation. It has one additional mutation in the spike protein compared to XBB1.5, which in lab studies shows increased infectivity and “potential increased pathogenicity”. It seems to be more immune evasive than XBB1.5 but there is no evidence for the moment that it causes more severe infections.
July 2023: The EG.5 subvariant, a descendant of the XBB lineage, now accounts for over 17% of cases in the US and has been rising in other countries also. The WHO has classified it as a variant of interest but says that it does not seem to pose more of a threat than other variants. No change in disease severity has been observed.
August 2023: A new subvariant called BA.286 has been identified in a handful of unrelated cases in a few countries (7 cases in 4 countries as of August 23). This variant is notable due to a high number of mutations (33 mutations in Spike, relative to its putative ancestor BA.2). It is difficult to predict the impact of such a large number of mutations, but significant antibody escape can be expected. Its identification in individuals without travel history suggests there is established international transmission, but it is not yet clear whether this variant will be able to outcompete currently circulating XBB variants.
November 2023: The WHO reclassified the BA.2.86 variant (also known as Pirola) and its offshoots (including JN.1) as a variant of interest since it is becoming increasingly prevalent worldwide. Despite the many mutations in Spike, its capacity to evade immunity does not seem to be as dramatic as when Omicron emerged. There is so far no indication that the disease is more severe.