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News • SARS CoV-2 B.1.621
WHO classifies Coronavirus "Mu" as new 'Variant of Interest'
The World Health Organization (WHO) has taken a closer look at coronavirus variant B.1.621. The strain, first encountered in January 2021 in Colombia, shows traits that could enable the virus to circumvent immune response to vaccination. As a result, the variant, named "Mu", has been classified as "Variant of Interest" (VOI).
Despite its prominence in Colombian new infection, the variant's global prevalence is low as of yet. "The Mu variant has a constellation of mutations that indicate potential properties of immune escape. Preliminary data presented to the Virus Evolution Working Group show a reduction in neutralization capacity of convalescent and vaccinee sera similar to that seen for the Beta variant, but this needs to be confirmed by further studies," the WHO states in its weekly epidemiological update. "Since its first identification in Colombia in January 2021, there have been a few sporadic reports of cases of the Mu variant and some larger outbreaks have been reported from other countries in South America and in Europe."
The WHO routinely monitors and assesses variants of SARS-CoV-2 regarding their potential impact on global health. Variations that increase transmission rates or showcases mechanisms to escape vaccination or medication efforts and other public health measures are labelled as Variants of Concern (VOCs) or Variants of Interest (VOIs). Currently, there are four VOCs (Alpha, Beta, Gamma and Delta) and five VOIs (Eta, Iota, Lambda, Kappa and Mu).
"Although the global prevalence of the Mu variant among sequenced cases has declined and is currently below 0.1%, the prevalence in Colombia (39%) and Ecuador (13%) has consistently increased," the WHO update continues. "The reported prevalence should be interpreted with due consideration of sequencing capacities and timeliness of sharing of sequences, both of which vary between countries. More studies are required to understand the phenotypic and clinical characteristics of this variant. The epidemiology of the Mu variant in South America, particularly with the co-circulation of the Delta variant, will be monitored for changes."
Source: World Health Organization