Why do viruses keep mutating?

Cover reporter Shao Meng

In the third year of the human war against the “epidemic”, the new coronavirus has not stopped its evolution and mutation.

Since March this year, the UK Health and Safety Agency (UKHSA) has reported three recombinant strains: XF, XE and XD. The World Health Organization pointed out in the report that early estimates indicate that the XE strain is more than the current global predominant strain. Omicron BA.2 has a 10% growth advantage;

On April 11, WHO added the new sub-variants BA.4 and BA.5 of the Omicron variant to the surveillance list;

On April 12, South Korea’s Central Epidemic Prevention and Control Headquarters stated that the first confirmed case of infection with the new coronavirus recombinant strain XL was found, and an epidemiological investigation is currently underway;

The New York State Department of Health said on April 13 local time that two new Omicron subtype variants, BA.2.12 and BA.2.12.1, were found in the state, accounting for about 80.6% of the state’s new crown infections.. ….

Will the new coronavirus continue to mutate? Does its pathogenicity decrease with the variant? What requirements does the mutated new coronavirus put forward for vaccine development? How should we respond?

Will the mutation of the new coronavirus continue?

The cover news reporter combed through the data of the WHO’s Cov-Lineages platform to track SARS-CoV-2 variants and found that since the outbreak of the new crown at the end of 2019, there have been more than 1,600 clearly reported variant lineages. In the face of successive new coronavirus variants, many people question: Will the new coronavirus continue to mutate?

“The new crown pneumonia virus is a single-stranded RNA virus. From a virological point of view, it is easier to mutate. As long as it has the opportunity to replicate, it will continue to mutate.” President of Shenzhen Third People’s Hospital, expert in disease prevention and control of the National Health Commission Lu Hongzhou, a member of the committee and an academician of the American Academy of Microbiology, said in an interview with a cover reporter that the virus has no mind, and the only way for it to exist is to use all the surrounding nutrients to synthesize its offspring and replicate its own “offspring”. The best way for the new coronavirus to mutate is to stop it from replicating.

There are many variants of the new coronavirus, but very few have become dominant strains.

Jin Dongyan, a professor and virology expert at the School of Biomedical Sciences at the University of Hong Kong, told reporters that any virus can mutate. Although the new coronavirus is very prone to mutation, its mutation rate is actually lower than that of SARS, influenza and HIV. “From the Wuhan period to the present, there have been thousands of mutant strains and hundreds of recombinant strains of the new coronavirus. But when we look back at the new crown epidemic, most of the strains are short-lived. Many strains may even be discovered. The opportunity is gone.” Jin Dongyan said that there is survival of the fittest among the new coronavirus strains, and only those with strong adaptability can survive.

He believes that the new coronavirus will still mutate in the future, but from the natural law of virus evolution and development, its mutation rate cannot become faster and faster, and the infection rate cannot increase indefinitely. “The new coronavirus is constrained by its own characteristics and changes in a ‘cage’.” Jin Dongyan said that the ultimate goal of the virus is to coexist with the host, and it will become more and more suitable for humans. But at the same time, recognize that the adaptation process is longer, and we will still be coexisting with the new coronavirus for a considerable period of time.

On March 1, in Central, Hong Kong, citizens wore masks to travel. Photo by Xinhua News Agency reporter Lu Binghui

Will the pathogenicity of the new coronavirus become weaker as it mutates?

As the new coronavirus mutates, will its pathogenicity gradually weaken?

WHO Director-General Tedros Adhanom Ghebreyesus said on March 30 that existing research shows that the most likely scenario is that the new coronavirus will continue to evolve, but as human immunity increases due to vaccination or infection, the new coronavirus will lead to The severity of the disease decreases over time. But he also suggested a worst-case scenario: the emergence of a more pathogenic and highly contagious variant, in which protection from previous vaccination or infection would rapidly diminish .

Citing known data, Lu Hongzhou said that the new coronavirus has been detected in 29 species of animals, which may in turn infect humans, and the virus can recombine in human cells. “There are too many uncertainties, so there is no Which scientist or theory says that the mutation direction of the virus must be from strong to weak.”

He believes that Omicron is highly contagious. Even if it has been infected in the past, it can be re-infected. It will inevitably include some elderly people or people who have not been vaccinated. The death rate may still remain high, so it must not be regarded as a “Big Flu”.

Jin Dongyan told reporters that most of the recombinant strains will die out quickly, and so far none of the recombinant strains can become the dominant strain in the world. Compared with recombinant strains such as XD, XF, XE, etc., we should be more alert to the sudden emergence of new mutants.

He said that the ultimate goal of the virus is to coexist with the host, and it will become more and more adapted to humans. The possibility of highly pathogenic variant strains cannot be said to be non-existent, but it is very low. The transmissibility may increase with the variation, but limited by its own characteristics, its transmissibility cannot be infinitely increased. Most coronavirus scholars believe that the four resident coronaviruses that only cause common colds in humans evolved from highly pathogenic predecessors, and that the new coronavirus may also lead to the same goal in the future. As long as human beings work together to control the epidemic and reduce the chance of the new coronavirus replicating, the chances of the virus mutating will also be reduced. With the advent of a new generation of vaccines, it remains to be seen whether the new coronavirus will disappear from humans like smallpox and polioviruses.

The virus keeps mutating, how to deal with it?

“It’s better to get a vaccine, an effective vaccine, and a better vaccine.” When talking about how to deal with the constantly mutating new coronavirus, Jin Dongyan repeatedly emphasized the role of vaccines. He said that the data of this round of Hong Kong epidemic has further proved the importance of vaccination. After the third dose of the vaccine, the infection rate, severe rate and mortality rate will be greatly reduced.

On April 12, the cover reporter attended the press conference of the Joint Prevention and Control Mechanism of the State Council in Beijing. At the meeting, Wang Huaqing, chief expert of the immunization program of the Chinese Center for Disease Control and Prevention, also pointed out that the latest research in Hong Kong shows that three doses of the new coronavirus vaccine can reduce the risk of severe illness and death by more than 90%.

In addition, another new study in Hong Kong on April 8 showed that among people over 60 years old, the relative risk of death caused by no vaccination was 21 times that of those who received two or more doses.

Lu Hongzhou told reporters that in order to block the mutation of the new coronavirus, it is still necessary to strengthen basic research. The virus is changing, but basic research on the virus will find some mechanisms that “remain unchanged”. “We can discover the mechanisms of viral immune escape, and now that we understand it, there are ways to prevent them from escaping.”

Lu Hongzhou emphasized the need to develop inhaled vaccines. “It can generate both cellular immunity and mucosal immune response where the virus invades the upper respiratory tract of the human body. The respiratory tract is the gateway for virus invasion. With immune protection at the first pass, the virus cannot enter or replicate. This is the future of vaccine development. direction.”

In addition to vaccines, Lu Hongzhou believes that the popularization and use of oral small-molecule drugs is also very important. “Basic research should be strengthened for vaccines and specific drugs. With effective vaccines and oral small-molecule drugs, the epidemic will be effectively controlled.”

How can individuals strengthen their protection against the constantly mutating new coronavirus?

At the press conference of the Joint Prevention and Control Mechanism of the State Council held on April 12, Wu Zunyou, chief expert on the immunization program of the Chinese Center for Disease Control and Prevention, told the cover reporter that whether the virus has become a new strain, or the two viruses have become heavy in the body To compose new virus mutations, we can all “remain unchanged”. For individuals, it is necessary to implement protective measures, including wearing masks, hand hygiene, social distancing, active vaccination, etc., to deal with the capricious phenomenon of virus mutation and reduce the risk of personal infection.

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