How strains appear
Viruses reproduce only inside a living cell, using its resources. To do this, they
There is no universally accepted nomenclature in the worldthe names of the strains, and the names used are quite arbitrary. As a rule, they consist of individual letters and numbers, which are written after the species name. For example, one of the most famous strains of E. coli is E. coli K − 12.
The virus tries to fix replication failures, but not always successfully. If a mutation gives the pathogen any life advantage, it can take hold.
Bacterial strain colonies Yersinia on the surface of agar-agar
At the moment, it is known that SARS-CoV-2accumulates mutations at about the same rate as the causative agent of influenza. Mutations in the genome of a new type of coronavirus almost always arise not due to random errors during copying, like in many other viruses, but as a result of damage or improper editing of an already finished copy of the RNA of the virus.
How new strains of COVID-19 are found
Samples of mucous membranes are taken from patients anddecode the genome of the pathogen. This information is loaded into common databases and compared. For example, the GISAID database contains more than two million coronavirus genomes from around the world. There is a tracker that visualizes which option was identified in which country.
By January 16, Rospotrebnadzor reported that it had come up with a special test that would identify the British strain. He will show the result 1.5 hours after the person took a smear.
More in-depth and complex tests are needed totell what strain the patient has. Now [using PCR tests] you can find out if a person has an active virus - there is a variant of COVID-19 or not. But this does not mean that it is generally impossible to determine a specific strain, it just takes more time and money.
Alexey Agranovsky, professor of Moscow State University and doctor of biological sciences
Therefore, in Russia, find out how many peoplehave contracted a coronavirus with a specific mutation, it is not yet possible, but random tests can be done to understand how widespread a certain strain of X is.
On the CoVariants website, using GISAID data, you can see which mutations distinguish the genome of a given variant. Thus, the delta variant has four significant mutations in the spike protein and two deletions.
The most dangerous variants of COVID-19
The WHO has ranked four options as dangerous: alpha, beta, gamma and delta.
The strain was first detected in October 2020 during the COVID-19 pandemic in the UK from a sample taken the previous month.
Since then, his chances of dominance have doubledevery 6.5 days (estimated generation interval). This correlates with a significant increase in the incidence of COVID-19 infection in the UK.
There is some evidence that this variant has a 30–70% increased transmissibility, in addition, preliminary studies suggest an increase in mortality.
However, as more happensmutations, a change in the vaccine may be required. SARS-CoV-2 does not mutate as quickly as influenza viruses, for example, and new vaccines that have proven effective by the end of 2020 are types that can be changed if necessary.
As of the end of 2020, bodieshealth experts and experts from Germany, the United Kingdom and America believe that existing vaccines will be as effective against the VOC-202012/01 strain as against the previous strains.
The strain was first discovered in South Africa, about whichwas reported by the South African Department of Health on December 18, 2020. The researchers and officials reported that the prevalence of this strain was higher among young people without any underlying medical conditions, and compared to other strains, it is more likely to cause serious illness in these cases.
Scientists noted that this strain contains several mutations that allow it to more easily attach to human cells.
On January 8, 2021, the Guardian announced that the vaccinePfizer and COVID-19 BioNTech have shown in tests involving 20 blood tests that it is capable of providing protection against the 501.V2 strain. Further research is needed to establish the exact degree of protection.
On February 24, 2021, the Moderna company announced the beginning of clinical trials of a new version of its vaccine. The new version is specially designed to deal with 501.V2.
The strain was first discovered in Tokyo on January 6, 2021years by the National Institute of Infectious Diseases (NIID). The new strain was discovered in four people who arrived in Tokyo from the state of Amazonas on January 2, 2021.
The new strain first appeared in July and was firstdiscovered in October, but at the time of publication (December 2020), although its frequency increased significantly, its distribution was still mainly limited to the state capital of Rio de Janeiro.
New was the mutation of the spike protein K417T, which allowsthe virus binds more tightly to human cells, and in some cases even avoids antibodies. In addition, the virus infects young people and pregnant women more strongly than the original.
On February 11, 2021, the head of the Brazilian Ministry of Health, Eduardo Pazuello, announced that this strain is three times more infectious than the "original" SARS-CoV-2.
In October 2020, line B.1.617.2 was first detected in India. In the second half of April 2021, the Indian Delta strain entered Russia.
On June 14, 2021, India was discovereda mutated variant of B.1.617.2, which is known as variant AY.1 or delta plus. Delta Plus is distinguished by the presence of the K417N mutation in the spike protein, which is capable of reducing the activity of antibodies in recovered and vaccinated people.
Indian Ministry of Health named three distinguishing features"Delta plus": increased contagiousness, enhanced ability to bind to receptors of lung cells and potential resistance to monoclonal antibody therapy.
By early July 2021, the World OrganizationHealth has recorded the delta strain in 98 countries with both high and low vaccination rates of the population, in many countries it is becoming dominant.
According to the Russian Consortium forBy sequencing the genomes of SARS-CoV-2 (Coronavirus Russian Genetic Initiative, CoRGI), the delta strain occupied slightly more than half (52%) in the samples obtained in St. Petersburg in May 2021, and in June 2021 - more than 90%.
Also, the "delta plus", identified in June last year in Nepal, belongs to the category of threatening. It has five mutations in the spike protein that make the virus very dangerous.
What options for COVID-19 scientists are watching
There are four more variants of SARS-CoV-2 on the WHO list that are of interest, but so far there is no reason to consider them more dangerous: Eta, Iota, Kappa, Lambda.
The so-called "lambda strain" SARS-CoV-2 for the first timeallocated to Peru at the end of last summer. Infections with the new strain have also been reported in Argentina and Chile. Subsequently, it spread to Germany, Spain, USA, Great Britain and several other countries.
The genome of the "lambda strain" contains a set of eightkey mutations that are believed to increase the infectivity of the virus. Brazilian scientists led by Priscila Wink from the Federal University of Rio Grande do Sul first recorded traces of the "lambda variant" of SARS-CoV-2 in Brazil and discovered a new variant of this version of the virus. Strain "lambda" found as of July 19 in 29 countries
The strain was identified in March last year in New York,it spread 35% faster. For some time successfully competing with alpha, scientists assumed that in combination with the E484K mutation in the spike protein, which helps to escape antibodies, this option would be dangerous. WHO has assigned him threatening status. But these predictions did not come true, and now he is simply being watched.
Will vaccines help against new strains?
There is no definite answer. The effectiveness of vaccines can be assessed in different ways:
- Track how the number of new cases changesinfection and hospitalizations. For example, in the UK, almost 88% of adults received one dose of the vaccine, 67% a second. The delta variant dominates in the country. According to official statistics, the incidence has increased over the past week by more than a third, the number of hospitalizations - by 46.8%.
- Conduct an experiment in the laboratory.Scientists create a pseudovirus with a spike protein, add one mutation after another to its genome, mimicking the variant under study. Then it is mixed with the blood serum of the fully vaccinated and dripped onto a human cell line susceptible to coronavirus. After a few days, the infected cells are counted.
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