On 30 August the World Health Organization (WHO) added a new variant of interest to the official list, the “Mu” variant, discovered in January 2021 and identified in 39 countries, including Italy. Here’s what we know about this lineage and why it needs to be closely watched by experts.
Coronavirus on cultured cells. Credit: NIAID
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The World Health Organization (WHO) divides the variants of the coronavirus SARS-CoV-2 into two main categories: le variants of interest (YOU), who are responsible for outbreaks in multiple countries and which have characteristics that can potentially make the virus more transmissible, virulent and / or able to evade neutralizing antibodies (both those induced by vaccines than from previous ones natural infections); and the variants of concern (VOC), or strains of the pathogen for which these characteristics have been confirmed by epidemiological investigations. At the time of this writing, four variants of concern are recognized – theAlfa, the Beta, the Gamma and the Delta (with the latter currently dominant in large parts of the world) – and five variants of interest, namely And, Iota, Kappa, Lambda e Mu. The latter has just been added to the list of YOU by the WHO, having shown that it can distinguish itself from the tide of lineages that continually emerge as SARS-CoV-2 spreads, replicates and mutates in infected hosts.
To describe the different characteristics of the Mu variant is Professor Paul Griffin, professor of Infectious Diseases and Microbiology at the University of Queensland, who has published an ad hoc article in The Conversation. The new variant of interest, inserted in the list on August 30, was discovered in January 2021 in Colombia and has been classified under the code name of lineage B.1.621. In early July, Public Health England (PHE) had identified her as FUN-21JUL-1. To date, as the WHO explains in the latest update of the “Weekly epidemiological update on COVID-19” dated 31 August, the Mu variant has been identified in 39 countries, Italy including (with just under 80 cases). The Mu variant also gave birth to a “daughter” variant called B.1.621.1 which has been detected in about twenty countries (in Italy 14 cases). In total, WHO points out, they have been uploaded 4,500 sequences of variant Mu on the international genetic database GISAID, 3794 relating to the “parent” strain (B.1.621) and 856 of the derivative (B.1.621.1). To date, the sequenced cases are less than 0.1 percent of the total and most of them are concentrated in Colombia (39 percent) and Ecuador (13 percent). Keeping in mind that this variant has been in circulation since the beginning of the year, at the moment its diffusion is contained and has not given rise to exploits such as the variants of concern Alfa and Delta, which respectively led the second wave of infections of last winter and the current third / fourth.
But why was the Mu variant classified as a variant of interest by the WHO? In addition to having given birth to outbreaks more or less significant in dozens of countries, the main reason lies in the fact that it owns one series of mutations already observed in other variants that have shown some resistance to antibodies and greater transmissibility. They are present in the genome of the Mu variant 21 mutations, nine of which of amino acids all located on the proteina S O Spike, the “biological pick” exploited by the pathogen to bind to ACE-2 receptor of human cells, break the cell wall, pour out theViral RNA inside and give life to the process replication, which underlies the infection / disease (called COVID-19). Among the most significant mutations are the E484K, a mutation of immune escape, the N501Y and the D614G, in addition to T95I, Y144S, Y145N, R346K, P681H and D109N. WHO underlines that the preliminary data relating to the Mu variant presented to the Virus Evolution Working Group show a certain capacity in reducing the neutralization activity both in serums of the convalescent that gods vaccine, not unlike the Beta variant (formerly South African), however, as stated by Professor Griffin, these are laboratory observations that must be verified in the real world, on the population. What is certain is that i Covid vaccines already approved byEMA and fromAIFA have proven to be effective against all variants out there.