SARS-CoV-2 Mu variant

Last updated

The Mu variant, also known as lineage B.1.621 or VUI-21JUL-1, is one of the variants of SARS-CoV-2, the virus that causes COVID-19. It was first detected in Colombia in January 2021 and was designated by the WHO as a variant of interest on August 30, 2021. [1] On 16 March 2022, the WHO has de-escalated the Mu variant and its subvariants to "previously circulating variants of concern". [2] [3]

Contents

The WHO said 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. [4] [5] Outbreaks of the Mu variant were reported in South America and Europe. [6] The B.1.621 lineage has a sublineage, labeled B.1.621.1 under the PANGO nomenclature, which has already been detected in more than 20 countries worldwide. [7]

Under the simplified naming scheme proposed by the World Health Organization, B.1.621 was labeled "Mu variant", and was considered a variant of interest (VOI), but not a variant of concern. [1]

Classification

Naming

In January 2021, the lineage was first documented in Colombia and was named as lineage B.1.621. [8]

On July 1, 2021, Public Health England (PHE) named lineage B.1.621 VUI-21JUL-1. [9]

On August 30, 2021, the World Health Organization (WHO) named lineage B.1.621 Mu variant. [1]

Mutations

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 D950N. [10] It has an insertion of one amino acid at position 144/145 of the spike protein, giving a total mutation YY144–145TSN. That mutation is conventionally notated as Y144S and Y145N because insertions would break a lot of comparison tools. It also features a frame-shift deletion of four nucleotides in ORF3a that generates a stop codon two amino acids. The mutation is labeled as V256I, N257Q, and P258*. The list of defining mutations are: S: T95I, Y144S, Y145N, R346K, E484K, N501Y, D614G, P681H, and D950N; ORF1a: T1055A, T1538I, T3255I, Q3729R; ORF1b: P314L, P1342S; N: T205I, ORF3a: Q57H, V256I, N257Q, P258*; ORF8: T11K, P38S, S67F. [11] Mutations in viruses are not new. All viruses, including SARS-CoV-2, undergo change over time. Most of these changes are inconsequential, but some can alter properties to make these viruses more virulent or escape the treatment or vaccines. [6]

On August 31, 2021, the WHO released an update which stated that the "Mu variant has a constellation of mutations that indicate potential properties of immune escape", noting that preliminary studies showed some signs of this but that "this needs to be confirmed by further studies." [12]

One such study conducted in a lab in Rome tested the effectiveness of sera collected from recipients of the BioNTech-Pfizer vaccine against the Mu variant, and found that "neutralization of SARS-CoV-2 B.1.621 lineage was robust", albeit at a lower level than that observed against the B.1 variant. [13]

Characteristic mutations of Mu Variant [10]
Gene Amino acid
ORF1a T1055A
T1538I
T3255I
Q3729R
ORF1b P314L
P1342S
S T95I
Y144S
Y145N
R346K
E484K
N501Y
D614G
P681H
D950N
ORF3a Q57H
del257/257
ORF8 T11K
P38S
S67F
N T205I

History

August 2021

August 6:

August 30:

September 2021

September 2:

September 3:

September 4:

September 7:

September 8:

September 9:

September 16:

September 18:

Statistics

Confirmed cases by country (as of November 3, 2023)
Country GISAID [38] outbreak.info [10] other sources
Flag of the United States.svg USA5,5506,550
Flag of Colombia.svg Colombia3,9954,974
Flag of Chile.svg Chile850958
Flag of Spain.svg Spain665690
Flag of Ecuador.svg Ecuador352447
Flag of Mexico.svg Mexico345435
Flag of Peru.svg Peru24027686 [24]
Flag of Canada (Pantone).svg Canada142162
Flag of the Dominican Republic.svg Dominican Republic115118
Flag of Aruba.svg Aruba9494
Flag of Italy.svg Italy8285
Flag of the Netherlands.svg Netherlands767646 [39]
Flag of Costa Rica.svg Costa Rica7374
Flag of the United Kingdom.svg United Kingdom716759 [40]
Flag of Puerto Rico.svg Puerto Rico5757
Flag of Belgium (civil).svg Belgium5151
Flag of Austria.svg Austria4949
Flag of Switzerland (Pantone).svg  Switzerland4848
Flag of Argentina.svg Argentina41421 [32]
Flag of the British Virgin Islands.svg British Virgin Islands4141
Flag of Jamaica.svg Jamaica333326 [29]
Flag of France.svg France2928
Flag of Mongolia.svg Mongolia2020
Flag of Portugal (official).svg Portugal2025
Flag of Curacao.svg Curacao1920
Flag of Brazil.svg Brazil172112 [33] [34] [35] [36]
Flag of Panama.svg Panama1616
Flag of Germany.svg Germany1516
Flag of Venezuela.svg Venezuela1515
Flag of Denmark.svg Denmark1112
Flag of Bolivia.svg Bolivia1010
Flag of Bonaire.svg Bonaire810
Flag of Poland.svg Poland88
Flag of Finland.svg Finland551 [37]
Flag of Haiti.svg Haiti56
Flag of Japan.svg Japan552 [16]
Flag of the United States Virgin Islands.svg U.S. Virgin Islands551 [26]
Flag of Ireland.svg Ireland444 [23]
Flag of Slovakia.svg Slovakia44
Flag of Sweden.svg Sweden44
Flag of Guatemala.svg Guatemala342 [18]
Flag of Hong Kong.svg Hong Kong333 [21]
Flag of Luxembourg.svg Luxembourg33
Flag of the Cayman Islands.svg Cayman Islands23
Flag of Israel.svg Israel22
Flag of Saint Vincent and the Grenadines.svg Saint Vincent and the Grenadines235 [28]
Flag of Sint Maarten.svg Sint Maarten23
Flag of Turkey.svg Turkey222 [27]
Flag of Barbados.svg Barbados11
Flag of the Czech Republic.svg Czech Republic11
Flag of Gibraltar.svg Gibraltar11
Flag of Liechtenstein.svg Liechtenstein11
Flag of Lithuania.svg Lithuania11
Flag of Malta.svg Malta11
Flag of Morocco.svg Morocco11
Flag of South Korea.svg South Korea113 [22]
Flag of the Turks and Caicos Islands.svg Turks and Caicos Islands11
Flag of Romania.svg Romania11
Flag of Greece.svg Greece116 [20]
Flag of the Republic of China.svg Taiwan111 [17]
 Total12,95215,090260

See also

References

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