Since its designation as a VOC by WHO on 26 November 2021, viruses part of the Omicron complex have continued to evolve, leading to descendent lineages with different genetic constellations of mutations. As transmission of these VOCs has been sustained, this has led to significant intra-VOC evolution. Delta reached almost 90% of all viral sequences submitted on GISAID by October 2021, and Omicron is currently the dominant variant circulating globally, accounting for >98% of viral sequences shared on GISAID after February 2022. Latest VOCs have largely replaced other co-circulating SARS-CoV-2 variants. At the present time, this expert group convened by WHO has recommended using letters of the Greek Alphabet, i.e., Alpha, Beta, Gamma, Delta which will be easier and more practical to be discussed by non-scientific audiences. When using this naming scheme and referring to the genomic sequence of SARS-CoV-2 identified from the first cases (December 2019), the term ‘index virus’ should be used.
To assist with public discussions of variants, WHO convened a group of scientists from the WHO Virus Evolution Working Group (now called the Technical Advisory Group on Virus Evolution), the WHO COVID-19 reference laboratory network, representatives from GISAID, Nextstrain, Pango and additional experts in virological, microbial nomenclature and communication from several countries and agencies to consider easy-to-pronounce and non-stigmatising labels for VOI and VOC.
The established nomenclature systems for naming and tracking SARS-CoV-2 genetic lineages by GISAID, Nextstrain and Pango are currently and will remain in use by scientists and in scientific research.
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