The World Health Organisation (WHO) has recently added Mu (B.1.621) to its list of Variants of Interest (VOI) for Covid-19, alongside another, C.1.2. Meanwhile, according to the Indian SARS-CoV-2 Genomics Consortium (INSACOG), India continues to primarily see the Delta variant and its sub-lineages. As a variant, C.1.2 is a sub-lineage of the C.1 variant and originated in South Africa, yet hasn’t achieved global dissemination.
Mu: A New Variant of Interest
Mu, or B.1.621, comes from a lineage of Covid-19 variants and was named using the Greek alphabet. It was first detected in Colombia in January 2021. Mu comes with a series of mutations, implying that it may have capabilities to escape immune responses. The variant has several substitutions affecting the Spike Protein in addition to experiencing changes in amino acids. Specific mutations like E484K, N501Y, P681H, D614G have been observed; these mutations have also been reported in other VOIs and Variants of Concern (VOC). Presently, Mu is the fifth ‘VOI’ under WHO’s monitoring. Other VOIs include Eta (B.1.525), Iota (B.1.526), Kappa (B.1.617.1), and Lambda (C.37).
The Criteria for Variants of Interest
For a variant to be classified as a VOI by the WHO, it must present certain genetic features that could potentially affect virus characteristics, including transmissibility and severity of disease. These changes can also lead to a higher ability for the virus to escape immune response, as well as cause difficulties for existing diagnostics or treatments. Further, a variant can be categorized under VOI if it can significantly transmit or cause multiple Covid-19 clusters across countries and pose an emerging risk to global public health.
Understanding Variants of Concern
A VOI can be promoted to a VOC if evidence shows that it is associated with increased transmissibility, virulence, or if it can decrease the effectiveness of public health efforts, diagnostics, vaccines, and treatments. As of now, four variants of the coronavirus have been designated as VOCs: Alpha (B.1.1.7), Beta (B.1.351), Gamma (P.1), and Delta (B.1.617.2), originating from the UK, South Africa, Brazil, and India respectively.
Mutation, Variant, and Strain: What’s the Difference?
During virus replication, there might be some instances where an exact copy of the virus isn’t produced, leading to slight differences in its genetic sequence. Such changes are known as mutations. Viruses with new mutations are referred to as variants, which could differ due to one or multiple mutations. When a variant displays different functional properties compared to the original virus and becomes established in a population, it qualifies as a new strain of the virus. It’s important to note that while all strains are variants, not all variants can be classified as strains.
