Highly transmissible and virulent strains of SARS-CoV-2
The term variant of concern (VOC) for
SARS-CoV-2, which causes
COVID-19, is a category used for
variants of the virus where mutations in their
spike protein receptor binding domain (RBD) substantially increase binding affinity (e.g., N501Y) in RBD-hACE2 complex (genetic data), while also being linked to rapid spread in human populations (epidemiological data).[1]
Before being allocated to this category, an emerging variant may have been labeled a variant of interest (VOI),[2] or in some countries a variant under investigation (VUI).[3] During or after fuller assessment as a variant of concern the variant is typically assigned to a lineage in the
Pango nomenclature system[4] and to clades in the
Nextstrain[5] and
GISAID[6] systems.
Decreased susceptibility to
antiviral drugs (if and when such drugs are available)
Decreased susceptibility to neutralizing
antibodies, either therapeutic (e.g., convalescent plasma or monoclonal antibodies) or in laboratory experiments
Ability to evade natural
immunity (e.g., causing reinfections)
Increased affinity for particular demographic or clinical groups, such as children or
immunocompromised individuals.
Variants that appear to meet one or more of these criteria may be labeled "variants of interest" or "variants under investigation" ('VUI') pending verification and validation of these properties. Once validated, variants of interest /VUI may be renamed "variants of concern" by monitoring organizations, such as the CDC.[3][7][10] A related category is "variant of high consequence", used by the CDC if there is clear evidence that the effectiveness of prevention or intervention measures for a particular variant is substantially reduced.[11]
Classifications by country
World Health Organization
The
WHO maintains a list of variants of global concern.[2] On 26 November 2021, the WHO added a fifth variant of concern, the
Omicron variant, previously known as B.1.1.529.[12] Omicron joins the
Alpha,
Beta,
Gamma, and
Delta variants.[citation needed]
Africa
The
NICD in
South Africa maintains a list of variants and testing facilities locally in collaboration with
KRISP.[13][14]
Europe
As of November 2021, the European Centre for Disease Prevention and Control declared four variants to be 'variants of concern': Beta, Gamma, Delta, and B.1.1.529 (named 'Omicron' after the reference was updated); Mu, Lambda and AY.4.2 were named as Variants of Interest (VOI), while there were 9 'Variants under monitoring'. 25 variants were described as 'de-escalated'.[15]
United Kingdom
As of November 2021, the United Kingdom has fifteen variants on its 'watch list', 4 with 'VOC' status and 11 rated as 'VUI'. Those designated 'VOC' were Alpha, Beta, Gamma, and Delta. In early December 2021, Omicron was added to the VOCs. Among the Variants under investigation is
'VUI-21OCT-01/ A.Y 4.2'.[16]
North America
Canada (via health-infobase.canada.ca)[17] and the United States (via the
CDC)[18] also maintain lists of variants of concern. As of early December, Canada was monitoring five variants of concern: Alpha, Beta, Gamma, Delta, and Omicron, while the US was monitoring two: Delta and Omicron.[19]
^
ab"Variants: distribution of cases data". GOV.UK. 28 January 2021. At "Differences between a Variant of Concern and Variant Under Investigation". Retrieved 19 February 2021. SARS-CoV-2 variants, if considered to have concerning epidemiological, immunological, or pathogenic properties, are raised for formal investigation. At this point they are designated Variant Under Investigation (VUI) with a year, month, and number. Following a risk assessment with the relevant expert committee, they may be designated Variant of Concern (VOC)
^CDC (11 February 2020).
"Emerging SARS-CoV-2 Variants". Centers for Disease Control and Prevention. Retrieved 4 January 2021. This article incorporates text from this source, which is in the
public domain.