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Viruses, like many microorganisms, reproduce by dividing their own cells. If the virus formed in this way differs in some characteristics from the “parent”, they speak of the emergence of a new strain. The emergence of new strains is a natural process that occurs with most viruses. The causative agent of COVID-19 was no exception.
To date, a huge number of strains of SARS-CoV-2 are known. Some of them have become widespread and recognized as significant (Alpha, Beta, Gamma, Delta). Others are less aggressive. One of the latest strains of SARS-CoV-2 is Mu. It is also known as B. 1.621. Despite the fact that so far it has not received mass distribution, it has already caused serious concerns for virologists.
Where and when did the Mu strain appear?
Virus mutations and the emergence of new strains are a natural reaction. In this way, pathogens adapt to new conditions for themselves. Mutations increase the chances of survival. In many cases, such changes have little effect on the basic characteristics of the virus. For example, you can become infected with different strains of influenza, but the course of the disease will be approximately the same. But there are also mutations that can affect the rate of spread of the virus, its resistance to the immune response. In addition, the complexity of the course of a disease caused by a mutated virus sometimes changes.
Since the beginning of the COVID-19 pandemic, the SARS-CoV-2 virus has mutated many times. The Mu strain was first discovered in January 2021 in Colombia. Since then, scientists have been closely watching how the new SARS-CoV-2 mutation will behave. The strain spreads slowly. But after Mu was found in 39 countries around the world at the end of August, WHO included it in the list of significant ones.
So far, Mu is responsible for approximately 0,1% of all COVID-19 cases. Carriers of a new variant of SARS-CoV-2 have been found in the UK, USA, Hong Kong, South Korea, and some countries of continental Europe. But most of the cases of infection occur in Colombia – about 39%, and Ecuador – about 13% of all recorded infections with the Mu strain. [1].
The virus in the Mu variant causes symptoms typical of COVID-19:
- fever;
- coughing;
- loss of smell and taste.
Most other variants of SARS-CoV-2 cause the same symptoms.
Why virologists are alarmed by the appearance of Mu
The Mu strain has been found to have mutations that allow it to evade immunity received after vaccination or suffered from COVID-19. The same feature has Beta, discovered earlier in South Africa. The researchers compared different modifications of SARS-CoV-2 and found mutations in the spike protein in the Mu variant that make the virus more resistant to antibodies. [2]. In addition, experts from Rome found mutations in it, which are also found in Alpha and Gamma variants. [3]. And according to the European Center for Disease Prevention and Control, Mu also carries a mutation characteristic of the Delta strain. [4].
Mutations in the Mu virus were also studied by specialists at Columbia University. They found changes in the set of amino acids in the spike protein, as well as a unique 146N insert, the effect of which on pathogenesis and contagiousness is still unknown. [5].
Russian experts also expressed their opinion about a possible scenario for the spread of the Mu strain. In particular, the candidate of medical sciences, immunologist Nikolai Kryuchkov, suggested that the spread of a new strain resistant to antibodies is associated with mass vaccination. Given that the strongest survive in the world of viruses, the COVID-19 pathogen has to adapt to new conditions – learn to bypass the immunity created by the vaccine. Hence the appearance of mutations. Although at the same time, the scientist noticed that even vaccines not adapted to mutated viruses still continue to work, albeit worse. [6].
Mu Vaccine Efficacy: Researchers’ Opinion
Despite the fact that mutations have been found in the Mu strain that allow the virus to evade acquired immunity, scientists do not undertake to unequivocally state that vaccines against it are powerless. Although in the scientific world there are different opinions on this matter.
Italian scientists conducted a study during which they tested the effectiveness of the BioNTech-Pfizer vaccine against the SARS-CoV-2 Mu mutation – B.1.621. As a result, experts found that the effectiveness of the vaccine against the strain, although lower compared to other variants of the virus, still has [3]. But at the same time, the results of a study were published in the scientific publication Lancet Infectious Diseases in August 2021, which showed that Mu is still able to withstand the immunity obtained as a result of vaccination. The same happens in the case of infection with the Beta version of SARS-CoV-2. [7].
American infectious disease specialists are also alarmed by the possibility of Mu bypassing antibodies [8]. And according to a study conducted by Japanese experts, the results of which, however, were not subjected to peer review, the Mu strain is about 7 times more resistant to the vaccine than the original version of the virus. [9].
It is too early to draw firm conclusions about what to expect from the Mu mutation. Epidemiologists around the world are watching the strain. It all depends on how the virus behaves in the future and whether the number of infected will increase. But there is also an encouraging moment. Despite the fact that a new variant of SARS-CoV-2 was discovered in January 2021, it has not become dominant in the world.
- Sources of
- ↑ WHO. – Weekly epidemiological update on COVID-19 – 31 August 2021.
- ↑ bioRxiv. – Ineffective neutralization of the SARS-CoV-2 Mu variant by convalescent and vaccine sera.
- ↑↑ Wiley Online Library. – A cluster of the new SARS-CoV-2 B.1.621 lineage in Italy and sensitivity of the viral isolate to the BNT162b2 vaccine.
- ↑ European Centre for Disease Prevention and Control. – SARS-CoV-2 variants of concern as of 23 September 2021.
- ↑ ScienceDirect.com. – Characterization of the emerging B.1.621 variant of interest of SARS-CoV-2.
- ↑ Lenta.ru. – An immunologist linked the spread of the “mu” strain of coronavirus with mass vaccination.
- ↑ The Lancet Infectious Diseases. – Rapid genome sequencing in hospitals to identify potential vaccine-escape SARS-CoV-2 variants.
- ↑ CBS News. – Fauci says Moderna boosters might not be ready by September 20.
- ↑ bioRxiv. – Ineffective neutralization of the SARS-CoV-2 Mu variant by convalescent and vaccine sera.
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