SARS-CoV-2 Variant Classifications and Definitions

Updated July 20, 2021

Key Points

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• Genetic variants of SARS-CoV-2 have been emerging and circulating around the world throughout the COVID-19 pandemic.
• Viral mutations and variants in the United States are routinely monitored through sequence-based surveillance, laboratory studies, and epidemiological investigations.
• A US government SARS-CoV-2 Interagency Group (SIG) interagency group developed a Variant Classification scheme that defines three classes of SARS-CoV-2 variants:
  • Variant of Interest
  • Variant of Concern
  • Variant of High Consequence
• The B.1.1.7 (Alpha), B.1.351 (Beta), B.1.617.2 (Delta), and P.1 (Gamma) variants circulating in the United States are classified as variants of concern.
• To date, no variants of high consequence have been identified in the United States.
• Laboratory studies suggest specific monoclonal antibody treatments may be less effective for treating cases of COVID-19 caused by variants with certain substitutions or combinations of substitutions in the spike protein.
  • L452R is present in B.1.526 (Iota), B.1.427 (Epsilon), and B.1.429 (Epsilon) lineages, as well as the B.1.617 (Kappa, Delta) lineages and sub-lineages.
  • E484K is present in B.1.525 (Eta), P.2 (Zeta), P.1 (Gamma), and B.1.351 (Beta), but only some strains of B.1.526 (Iota) and B.1.1.7 (Alpha).
  • The combination of K417N, E484K, and N501Y substitutions is present in B.1.351 (Beta).
  • The combination of K417T, E484K, and N501Y substitutions is present in P.1 (Gamma).
• P.2 (Zeta) has been removed from the variants of interest list due to declining prevalence and very few detections in recent months. In addition to variants of interest and variants of concern, CDC continues to monitor all variants circulating within the United States.

 

Viruses constantly change through mutation. A variant has one or more mutations that differentiate it from other variants in circulation. As expected, multiple variants of SARS-CoV-2 have been documented in the United States and globally throughout this pandemic. To inform local outbreak investigations and understand national trends, scientists compare genetic differences between viruses to identify variants and how they are related to each other.