Variant Mu, the new strain that is already raising the alarm among local specialists

The declaration by the World Health Organization (WHO) as a variant of “Mu” interest for the coronavirus lineage first identified in Colombia this week has sounded the alarm in Latin America and, although the delta continues to be predominant and the most disturbing one around the world, experts stressed that “you need to keep a close eye on Mu’s news and see how it interacts with others circulating in the country.”

At present, as mentioned, the Delta variant continues to be the one that generates the greatest concern in the world: it has been responsible for dramatic situations like the health crisis in India and it has spread to hundreds of countries. . “And it moved the virus circulating where it entered, generating new waves,” warns virologist Humberto Debat.

Evidence

Debat, who is a member of the Argentinian SARS-CoV-2 Genomics Project (PAIS), recalled that “there is ample evidence that Delta is the most transmissible variant, it doubles hospitalization rates, while vaccines are less effective in protecting against the contagion of this variant, although the levels of coverage against severe cases remain very high. ”However, he explained that one must be attentive to what is happening with the Mu“ because as we have seen during the previous waves, the landscape of variations at the Latin American level has had a great impact on Argentina. Seeing that to date Mu represents 14% of cases in Chile (which had a scenario variants very similar to ours), this implies that there is a probability that it will enter our country and increase its frequency ”.

On August 31, WHO published its weekly epidemiological update report in which it reported having incorporated as a variant of interest the B.1.621 line first identified in January in Colombia, which it designated by the letter Greek Mu.

The references

“The Mu variant has a constellation of mutations that indicate potential immune evasion properties. Preliminary data presented to the Virus Evolution Working Group shows a reduction in the neutralizing capacity of sera from convalescent and vaccinated patients similar to that observed for the Beta variant (identified in May 2020 in South Africa), but this needs to be confirmed by studies. studies. additional, ”the agency said in the document.

In this sense, Debat argued that “what has been said by the WHO, which the same organization has indicated needs to be reconfirmed and is not yet in any scientific publication, is a big red flag because Beta is the variant with greater evasion or immune. escape.

According to the WHO, “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 steadily increased” .

According to what the Argentinian virologist describes, “we also know that it represents 14% of cases in Chile; that is, in the last time it began to spread to different countries in Latin America and increase its frequency; this is not minor because replication in other regions implies that it is independent of the situation and therefore that it is a “property” of the virus ”.

For her part, biochemist Josefina Campos, coordinator of the Anlis-Malbrán genomics and bioinformatics platform, assured that “it is difficult to say which variant should cause the most concern in Argentina because the behavior of each will depend on many factors, including how it interacts with the variants going around. The Delta is the majority in the world and it has a better chance of entering, but we will have to see how this relationship is established, which is dynamic ”.

Little data

Regarding Mu, Campos indicated that there is still little data, but we know that it has become very widespread in Colombia and Ecuador, so “we must take into account that what we see are the information about the sequences he shares but not us. to know what the methodology of this surveillance is ”. In principle, according to biochemistry, both in Colombia and Ecuador “the delta is very low, but it would be hasty to say that this is the result of the way they competed, we will have to wait a bit to see what happens when they live in the same territory. “

According to the latest report from the Ministry of Health on epidemiological surveillance in the country, carried out by the PAIS Project and Anlis-Malbrán, the most common variant in Argentina is Gamma (defined as worrying by the WHO and identified for first time in Manaus, Brazil) with a percentage close to 60% of the samples. It is followed by Lambda (defined as of interest and said Andean) with approximately 20%; while the Alpha (UK) does not reach 10%.

“What is today the Mu variant was already detected in August in sporadic cases in the city of Buenos Aires, in some travelers and two or three unrelated cases; it was found as part of the systematic surveillance carried out in the city, ”said Mariana Viegas, researcher at Conicet and coordinator of the PAIS project.

However, he stressed that to say that there is community circulation of a variant “it must be systematically detected over time and there must be a risk that the population will acquire it in the community, which is not. not yet the case with Mu “.

According to Campos, in the meantime, the Malbrán had detected the line which is now called Mu in April and “they had already observed the constellation of mutations which were of marked interest”.

Another news this week was the public announcement by South African health authorities that they were monitoring a new variant, “C.1.2”, which has yet to be classified by the WHO.

“It is a variant which has a large number of mutations: only the Spike protein has more than 12 and in total it has around 59 mutations compared to Wuhan (China); then this is one of the most different versions of the virus from the reference one; but the good news is that distinctive epidemiological behavior is not observed, “described Debat, who also clarified that” so far it does not extend geographically or chronologically and only 101 samples have been reported in the world “.

Finally, Campos recalled that “having the greatest amount of population with the two doses is what will allow us to better face the Delta variant in the event that it starts to have a majority community circulation. We have seen that most vaccines offer very good two-dose protection against Delta in terms of prevention of hospitalizations and deaths ”.