June 16, 2024

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Why can COVID-19 Delta mutant virus spread so quickly and fiercely?

Why can COVID-19 Delta mutant virus spread so quickly and fiercely?

Why can COVID-19 Delta mutant virus spread so quickly and fiercely? Scientists from Cambridge University will take you to understand it.


The new coronavirus has already cost many people their lives. However, its mutant strain is more powerful, and its transmission and toxicity far exceed the original new coronavirus.

This has aroused widespread concern in the scientific community. Through countless experiments and studies, they have tried to explore the characteristics of the mutant strains, and gradually developed effective treatment methods.

Recently, a group of researchers from the University of Cambridge has carried out research on the delta mutant strain. What kind of help will this bring to all walks of life in dealing with such a ferocious virus?

The delta variant is a variant strain of the new coronavirus that was first discovered in India by the World Health Organization in May 2021. It has now been determined to be one of the driving factors of the second wave of the epidemic in India. Earlier, the virus variant only appeared in parts of India. Due to various reasons, the virus has now spread to 92 countries.

Recently, an international research team at the University of Cambridge has made new discoveries about the Delta mutant strain: the delta variant of the COVID-19 virus is very likely to spread through its ability to evade neutralizing antibodies and increasing infectivity.

They published the results of this research in an article titled “SARS-CoV-2 B.1.617.2 Delta variant replication and immune evasion” in “Nature” magazine:

Why can COVID-19 delta mutant virus spread so quickly and fiercely?

As the new coronavirus continues to replicate, errors in its genetic composition cause it to mutate. Some mutations can even make the virus more transmittable and more contagious; some mutations can also help the virus evade the immune response, thereby reducing the effectiveness of the vaccine’s protective effect on people.

Other mutations have little effect on the virus and will not bring much change to the virus. Among these Delta Covid-19 mutant strains, one of them named B.1.617.2 was first discovered in India at the end of 2020; since then, it has spread to the world-in the UK, almost all Covid-19 patients have Is infected with this strain.

Professor Ravi Gupta of the Institute of Therapeutic Immunity and Infectious Diseases at the University of Cambridge is one of the senior authors of this study. He explained: “By combining the experiments we conducted with the epidemiological theory of breakthrough infections in vaccines, we proved Delta variants have stronger replication ability and transmission power than other common variants.

There is also evidence that for people who have been infected with the COVID-19 virus and those who have been vaccinated with the COVID-19 vaccine, the neutralizing antibodies produced in their bodies are all It has lost a lot of effectiveness in defending against this delta mutant strain. These factors are likely to cause the devastating outbreak in India in the first quarter of 2021.

As many as half of the COVID-19 patients were infected before then. The early mutant strains of COVID-19. It can be seen that the toxicity and infectious strength of the delta variant far exceed the original COVID-19 virus and its early mutant strains.”

In order to study how the delta variant escaped the immune response so easily, the scientists collected some blood samples, extracted serum from these blood samples, and analyzed them in detail. These blood samples come from people who have been infected with the COVID-19 virus, or those who have been vaccinated with any of the Oxford/Pfizer/AstraZeneca COVID-19 vaccines.

These immune sera collected by them all contain antibodies produced by previous new coronavirus infections or through vaccination. After comparison and research, they found that, compared to the sensitivity of the early mutant strain of the COVID-19 Alpha to these two immune serums, the delta mutant strain:

Immune serum for individuals who have been infected with the new coronavirus-sensitivity has been reduced by 57%;

The immune serum of individuals who have been vaccinated with the COVID-19 vaccine-sensitivity is reduced by 80% (that is, for an individual who has been vaccinated with the COVID-19 vaccine, he still needs to produce 8 times the number of antibodies in his body in order to successfully block the delta mutation virus. Strain)

Consistent with this data is a survey and analysis of more than 100 infected medical staff from three hospitals in Delhi, India. From this analysis, they found that almost all of these infected people were vaccinated with the COVID-19 vaccine, but they were still being vaccinated. The delta mutant strain is infected, and the defense effect of the vaccine is almost ineffective against the delta virus; moreover, the spread of the delta mutant strain among vaccinated persons exceeds that of the alpha mutant strain.

The new coronavirus is a type of coronavirus, so named because the spike protein on its surface makes it look like a coronavirus. Spike protein binds to ACE2, which is a protein receptor on the surface of cells in our body. Both the spike protein and ACE2 are then cleaved, allowing the genetic material of the virus to enter the host cell. The mechanism by which the virus manipulates the host cell allows the virus to replicate and spread.

Using 3D respiratory organoids (a “mini-organ” cultured from respiratory cells) to simulate the behavior of the respiratory tract, the team studied what happens when the virus reaches the respiratory tract. Under safe conditions, the research team used a live virus and a “pseudovirus” (a synthetic virus that mimics key mutations of Delta virus) to infect organoids. They found that, compared with other variants, the delta mutant strain is more effective when it enters the cell because it carries more cleavage spikes on its surface. Once inside the cell, the mutated gene can also replicate better. Compared with other mutations, these two factors give the virus a selective advantage and help explain why it has become so dominant. Dr. Partha Rakshit from the National Center for Disease Control in Delhi, India, is the senior author of the study. He said: “This delta mutant virus has spread widely and has become the main mutant virus affecting the world. The mutated virus spreads faster and is more infectious. It can better escape the existing immune response. However, for people who have been infected with COVID-19 or have been vaccinated against COVID-19, even if they cannot avoid the delta virus, However, their risk of suffering from moderate and severe illnesses has been reduced to a certain extent.”

Professor Anurag Agrawal from the Institute of Genomics and Integrative Biology of the CSIR Institute of Genomics and Integrative Biology in Delhi, India, is the co-senior author of the study. The problem. Although their own infection symptoms may be mild, the virus they carry may spread to other places, infecting people with relatively weak immune capabilities. Patients who are in the hospital or hospitalized are also vulnerable to infection by these medical staff.

This is a very risky thing, no doubt, this is a vicious circle. Therefore, we believe that it is very necessary to vaccinate the medical staff as soon as possible. In this way, more medical staff will gain immunity against the delta mutant virus, so as to prevent the virus from being transmitted to patients in the hospital again. Not only that, in the post-epidemic period, all regions still need to continue to strictly implement the COVID-19 prevention and control measures. “

(source:internet, reference only)

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