Variants galore
Mutations, variants, and new waves of infection
Many variants of the SARS-CoV-2 have emerged throughout the pandemic.
Most disappeared quickly because they were unable to compete with other circulating variants. However, some have managed to displace previously circulating variants, because they are either more inherently transmissible, better at evading vaccine immunity, or capable of causing reinfections. This is why each new variant of concern has caused a new wave of infections at the regional or global level.
A viral glossary
with some helpful definitions
Five variants of concern have been identified since the start of the pandemic






Figure 1. SARS-CoV-2 VOC depicted in a tree scaled radially
by genetic distance nextstrain.org
Date:
Current situation
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.
References to other useful sources
From official assessments to news features
Additional information
- Tracking SARS-CoV-2 Variants, WHO
- SARS-CoV-2 variants of concern, ECDC
- Tracking Omicron and Other Coronavirus Variants, New York Times (although not updated recently)
Further readings:
- Beyond Omicron: what’s next for COVID’s viral evolution, Nature
- Mutants, Variants, Recombinants and Other Figurants: Five Definitions and Five Key Concepts to Better Understand the Evolving Pandemic (Health is Global Blog)
- Big COVID-19 waves may be coming, new Omicron strains suggest, Science.
- SARS-CoV-2 evolution, post-Omicron, Virological.org