Omicron evolves again! Multiple new variants spread in the United States, experts: herd immunity may no longer apply

Since the COVID-19 outbreak, the virus has continued to evolve, from Alpha to Delta to Omicron, with new mutants appearing every few months on average. And various virus variants will divide and evolve into different subtypes. For example, Delta, there are as many as 200 subtypes, and the same is true for Omicron.

Recently, two new subtype virus variants of Omicron appeared in South Africa , bringing a fifth wave of epidemics locally.

1. South Africa ushered in a new round of outbreaks

According to media reports, as of the evening of May 7, local time in South Africa, the number of newly confirmed cases of COVID-19 in South Africa within 24 hours was 8,524, and the positive detection rate of the virus was as high as 31.1% , which was a record high of 34.9% last year . On May 11, South Africa reported 10,017 new confirmed cases of COVID-19 within 24 hours, the first time this year that the number of confirmed cases in a single day exceeded 10,000 .

At least 31 out of every 100 people tested are confirmed, which means the COVID-19 virus is spreading rapidly in the community .

South African epidemiologists say that South Africa is currently experiencing a fifth wave of the epidemic . At the beginning of April, South Africa just announced the lifting of the national disaster state that had lasted for more than two years. As a result, the epidemic rebounded, and the situation was not optimistic.

South Africa, as one of the starting locations of Omicron, has become the vane of the global COVID-19 epidemic . In November last year, the new mutant strain B1.1.529 of Omicron was first reported in ZBotswana, South Africa, and the BA.1 subtype strain became the mainstream virus at that time.

In February of this year, BA.2 replaced the dominance of BA.1. In a new round of outbreaks in South Africa, the new subtype strains BA.4 and BA.5 of Omicron became the dominant strains. So far, these two subtypes of the virus have been found in more than 20 countries and regions around the world, especially the United States.

Recently, new variants BA.4 and BA.5 have also begun to spread in the United States , but BA.2 is still the mainstream virus strain, and the next generation of BA.2, BA.2.12.1, is also spreading rapidly, and its spread is faster than BA.2 is 25% higher and has accounted for 52.3% of COVID-19 cases in New York, New Jersey and Connecticut. Facing the constant mutation of the COVID-19 virus, Fauci , the chief medical adviser of the United States , said in an interview that the traditional concept of herd immunity may no longer apply to the COVID-19 virus .

2. Continuous evolution, new strains have stronger escape ability

The BA.4 and BA.5 mutant strains that led to a new round of outbreaks in South Africa were derived from BA.2 and had stronger transmission ability than BA.2, BA.4 and BA.5 . The primary cause of mass infection.

There is optimism that as the COVID-19 virus continues to mutate, its harm will gradually decrease and its mutation patterns become more predictable, but we seem to be overlooking its "evolutionary" ability.

On May 6, the journal Nature published a new research article on BA.4 and BA.5 mutants.

Virus evolutionary biologist Jesse Bloom believes that the new BA.4 and BA.5 variants are more transmissible, partly because they are inherently better at transmission, and partly because the new mutants They are more prone to immune escape . They are better at evading the immune protection brought about by prior infection and vaccination. They can infect people with prior immunity , so they are prone to mass infection.

Bloom's team had previously found that both BA.4 and BA.5 carry a key mutation called F486V in their spike protein, which is responsible for infection and immune responses, that helps the mutants evade viral blockade Antibody.

The experimental results of the team of Academician Xie Xiaoliang of Peking University also found that the antibodies produced by BA.1 infection have a low protective effect on BA.4 and BA.5 , and BA.4 and BA.5 have certain immune escape ability .

3. Why is the super-mutated COVID-19 virus always born in South Africa?

From Beta to Omicron, as well as a variety of mutant branches, many were first discovered in South Africa and caused widespread infection, which makes people wonder why mutant viruses are always born in South Africa?

First of all, South Africa is the country with the most serious HIV epidemic in the world. The number of people infected with HIV is close to 8 million, ranking first in the world, and the HIV prevalence rate of adults is as high as 20%.

HIV, whose scientific name is human immunodeficiency virus , weakens the immunity of infected people, making them more susceptible to infection by other pathogens. As a result, HIV-infected patients can survive longer in the body after being infected with COVID-19 , and these patients become "Petri dishes" that increase the odds of the COVID-19 virus.

Secondly, with a total population of more than 60 million, South Africa is the 24th most populous country in the world and one of the countries hardest hit by COVID-19. Due to the huge base of infection with COVID-19 , the chance of generating new mutant strains will also be much greater.

Furthermore, the COVID-19 vaccination rate in South Africa is low , the overall vaccination rate is less than 50%, and only 45% of adults are fully vaccinated, making most of the population susceptible to COVID-19, the virus is not easy to clear, and increased virus mutation probability.

Of course, the ability to discover new variants of the virus first shows that South Africa has a strong ability to monitor viruses. South Africa is one of the few well-developed countries in Africa, with a strong scientific and economic foundation, and its virus surveillance capabilities are even stronger than many developed countries.

All in all, we cannot underestimate the harm of the COVID-19 virus prematurely. Active prevention, vaccination, and exercise to improve immunity are the best strategies.

References:

[1] The positive detection rate of COVID-19 in South Africa is the highest in history, or it may enter the fifth wave of the epidemic. CCTV Finance, 2022-05-08

[2] Omikron re-evolves! Multiple new variants are spreading in the United States, infectious disease experts: virus mutation is faster and wider than we expected. Red Star News, 2022-05-02

[3]Are COVID surges becoming more predictable？ New Omicron variants offer a hint.Nature 605， 204-206 (2022)

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