WHO names new strain Omicron and classifies it as worry variant

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The B.1.1.529 strain of the new coronavirus was classified as a variant of concern by the World Health Organization (WHO) this Friday (26). The decision is the result of an urgent meeting called by the WHO working group on Covid-19. In the statement, WHO also defined the technical name of the new variant: Omicron.

First identified in Botswana, southern Africa, the strain has worried scientists because it has many mutations that could confer advantages to the virus. The strain has also been found in South Africa and Hong Kong. So far, there are no records of the variant in Brazil.

Understand the three classifications of variants by WHO

The World Health Organization (WHO) carries out continuous global monitoring of variants of the new coronavirus. The strains are classified into different levels, considering aspects of transmissibility and health risk.

There are three classifications “concern variants”, “interest variants” and “under monitoring”.

The classification of “variants of concern” gathers the strains of the new coronavirus that show changes that can affect the properties of the virus, with one or more implications, including increased transmission capacity or disease severity, in addition to impacts on efficacy of vaccines, drugs and diagnostic methods.

Currently, Alpha (B.1.1.7), from the United Kingdom, Beta (B.1.351), from South Africa, Delta (B.1.617.2), from India, the Gamma ( P.1), from Brazil, and B.1.1.529, from Botswana.

A strain of SARS-CoV-2 is considered a variant of interest when it has mutations in the genetic material with established or suspected virus behavior implications, such as high incidence of transmission in one location, multiple lineage-related cases, and detection in multiple countries, for example. Therefore, they are monitored and can be reclassified as “concern variants”.

The strains Lambda (C.37), originating in Peru, and Mu (B.1.621), detected in Colombia, are classified as variants of interest.

The classification “under monitoring” is intended for strains with genetic alterations suspected of affecting the characteristics of the virus with some indication of future risk, but whose evidence of epidemiological impact is not clear at the moment. For these variants, which are currently eight, improved monitoring and continuous evaluation until new evidence is required.

From the identification, carried out through the genomic sequencing of the virus, scientists seek to answer different questions such as transmission capacity, increased lethality and whether there is any kind of reduction in the effectiveness of the vaccines developed against Covid-19.

So far, scientists have detected that the B.1.1.529 variant has several mutations, which may indicate advantages to the virus, such as a potential greater transmissibility and the escape of antibodies.

However, further studies are needed to answer whether the new variant could have any impact on the effectiveness of the Covid-19 vaccines in use in the world.

large number of mutations

The B.1.1.529 variant has a wide range of mutations. In isolation, these mutations can both bring advantages to the virus, such as a greater ability to transmit or escape from the immune system, or not represent any kind of gain for the microorganism.

“What is most striking is that the variant has a large number of mutations, there are at least 32. It has several mutations that we have already seen in other variants that were important over time, such as the Alpha variant”, explains the virologist Fernando Spilki, researcher at the Feevale University, in Rio Grande do Sul.

According to the researcher, in addition to mutations, the new variant has a characteristic technically called deletion. Because they are very simple structures, viruses have a great capacity for modification. Among these genetic changes, deletions arise, which are characterized by the removal of one or more nucleotides (which are the building blocks that make up RNA or DNA) from a gene.

The virologist explains that the variant has at least three deletions in the genetic material of the Spike protein, which is used by the virus to invade human cells, a fundamental part of the Covid-19 infection process.

“One deletion that caught my attention was the height of amino acids 69 and 70, which was found in the Alpha variant, identified in the UK. The variant also has the N501Y mutation, very characteristic of the Gamma variant, which also occurred in the Beta variant strains. It also has the E484A mutation, which demonstrates that the strain is ‘mutating’ in several ‘sites’ that we had already mapped over time”, he explains.

What is known about transferability

One of the main concerns of scientists with the emergence of a new variant is to find out if there is greater transmissibility, which could lead to Covid-19 outbreaks.

According to the virologist at the University Feevale, Fernando Spilki, further studies are needed to answer the question regarding the B.1.1.529 variant. However, the specialist points out that the strain has been widely disseminated in the places where it has been detected so far.

“In places where the variant occurred, in the last two weeks, it has evolved to 90% of detections, including places where the highly transmissible Delta variant had already spread and was causing an increase in cases. The B.1.1.529 variant, even so, today predominates with 90% of detections”, explains Fernando.

Impact on vaccine efficacy remains unknown

The researcher Fernando Spilki considers that understanding the impacts of mutations on characteristics such as transmissibility, lethality and effectiveness of vaccines against Covid-19 depends on additional studies.

“These mutations do not mean that we are in a critical situation. We need to test, both in vitro and in vivo, which are the effects of this accumulation of mutations, it is something that needs to be investigated”, he adds.

According to the virologist, South Africa has an efficient genomic sequencing program for the new coronavirus samples, which allowed the identification of the new variant even with a low number of cases.

However, the rapid increase in the number of cases throughout November in Gauteng province, where Johannesburg is located, has drawn the attention of local health authorities.

Genome sequencing revealed that the B.1.1.529 variant was responsible for all 77 virus samples analyzed in Gauteng, collected between 12 and 20 November. Hundreds of other samples are currently being analyzed.

Reference: CNN Brasil

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