The SARS-CoV-2 Mu Variant of Interest, Also Known as Lineage B.1.621 (VUI-21JUL-1)

Scientifically accurate atomic model of the external structure of SARS-CoV-2. Each “ball” is an atom.

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Mu Variant was first detected in Colombia in January 2021 and designated by the WHO as a variant of interest on August 30, 2021. The WHO indicated the variant has mutations that indicate a risk of resistance to the current vaccines and stressed that further studies were needed to better understand it. Outbreaks of the Mu variant were reported in South America and Europe. The lineage B.1.621 has a sublineage, labeled B.1.621.1 under the PANGO nomenclature, which has already been detected in more than 20 countries worldwide.

SARS-CoV-2 Mu variant – Wikipedia

More than 5,278 cases of the Mu variant have been identified worldwide through genomic sequencing, according to Outbreak.info. The U.S. has identified more then 2,300 of these cases, with 400 in California.

Mu Variant was first detected in Colombia in January 2021 and designated by the WHO as a variant of interest on August 30, 2021. The WHO indicated the variant has mutations that indicate a risk of resistance to the current vaccines and stressed that further studies were needed to better understand it. Outbreaks of the Mu variant were reported in South America and Europe. The lineage B.1.621 has a sublineage, labeled B.1.621.1 under the PANGO nomenclature, which has already been detected in more than 20 countries worldwide.

The Mu genome has a total number of 21 mutations, including 9 amino acid mutations, all of which are in the virus’s spike protein code: T95I, Y144S, Y145N, R346K, E484K or the escape mutation, N501Y, D614G, P681H, and D109N.

Transmissability: Likely Increased.
Virulence: Likely Increased.
Antigenicity: Mu variant has mutations that have the potential to evade immunity provided by a previous COVID-19 infection or vaccination.
Spread: Outbreaks of the Mu variant were reported in South America and Europe. The lineage B.1.621 has a sublineage, labeled B.1.621.1 under the PANGO nomenclature, which has already been detected in more than 20 countries worldwide.

Global Positive Samples Sequenced: 3,256,369

B.1.621 Sequenced: 3,624

% of Global Samples Sequenced: 0.11%

Distribution of B.1.621 Sequences Top 5 Countries: United States of America 46.0%, Colombia 13.0%, Mexico 10.0%, Spain 10.0%, Ecuador 4.0% – 3624

Lineage:

Distribution of B.1.621.1 Sequences Top 5 Countries: United States of America 63.0%, Spain 13.0%, Austria 5.0%, Dominican_Republic 5.0%, Switzerland 3.0% – 898

Updated September 2021

Amino acid mutations of SARS-CoV-2 Mu variant plotted on a genome map of SARS-CoV-2 with a focus on Spike.

Stanford HIVDB Team

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