Wednesday, May 05, 2021

CDC Update On SARS-CoV-2 Variant Classifications and Definitions - Adds 5 VOIs To List



#15,942

Just as we've seen in the UK (see last week's UK PHE COVID Variant Update - Adds 12th & 13th Variant To Watchlist), the CDC continues to monitor scores of major and minor COVID variants in the United States and to add emerging variants to their VOC (Variant of Concern) and VOI (Variant of Interest) watchlist. 

For the past couple of months, the CDC has selected 8 variants for closer monitoring:
  • The B.1.1.7, B.1.351, P.1, B.1.427, and B.1.429 variants circulating in the United States are classified as VOCs.
  • The B.1.526, B.1.527, and P.2 variants circulating in the United States are classified as VOIs. 
Today the CDC has updated their list, adding five more variants to their VOI list (B.1.526.1, B.1.617, B.1.617.1, B.1.617.2, B.1.617.3).  Notably, 4 of the 5 new variants are all related to the Indian Variant (B.1.617) that has caused so much concern over the past few weeks. 

As of their last biweekly update (see CDC U.S. Variant Update: B.1.1.7 Continues To Gain Ground In The United States), published a little over a week ago,  B.1.617.x variants weren't even on their list of top 20 variants in the United States (see chart below).
 


Excerpts from the CDC update, including a portion of the table on the Indian variant - published this morning - follow:
SARS-CoV-2 Variant Classifications and Definitions

Updated May 5, 2021

Key Points:
  • 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 interagency group developed a Variant Classification scheme that defines three classes of SARS-CoV-2 variants:
  • The B.1.526, B.1.526.1, B.1.525, B.1.617, B.1.617.1, B.1.617.2, B.1.617.3, and P.2 variants circulating in the United States are classified as variants of interest.
  • The B.1.1.7, B.1.351, P.1, B.1.427, and B.1.429 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.
  • In laboratory studies, specific monoclonal antibody treatments may be less effective for treating cases of COVID-19 caused by variants with the L452R or E484K substitution in the spike protein.
    • L452R is present in B.1.526.1, B.1.427, and B.1.429.
    • E484K is present in B.1.525, P.2, P.1, and B.1.351, but only some strains of B.1.526 and B.1.1.7.
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.

Despite the dire reports from India in recent weeks, it isn't clear how much of their crisis is due to any enhanced traits of the B.1.617 variant, and so - for now, at least - the UK and the United States have not listed them as VOCs. 

We should be getting new bi-weekly surveillance numbers from the CDC in the next week or so, and we may begin to see some or all of these new variants included in that report as well. 

Stay tuned. 

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