On November 9, 2021, South Africa first detected a new coronavirus B.1.1.529 variant from case samples and notified the World Health Organization (WHO). In the following two weeks, this variant became the absolute dominant variant of new crown infection cases in Gauteng, South Africa, with rapid growth. On November 26, the World Health Organization defined it as the fifth "variant of concern" and named it after Omicron.
As of press time, more than 80 countries and regions, including South Africa, Israel, Belgium, Italy, the United Kingdom, Austria, and Hong Kong, China, have found patients or asymptomatic infections with this variant. For a while, the whole world talked about "Austria", and maybe after learning the truth about Omicron, everyone will be calm.
Variation and origin of Omicron
After the alpha, beta, gamma, and delta variants of concern, which may have serious consequences, Omicron became the fifth variant of concern, because it had more genetic mutations than previous variants.
A total of 50 mutations have appeared in the genes of the Omicron variant (or Omicron for short), of which 32 are mutations in the spike protein that can bind to human cells and invade cells. The most sexual delta variant (referred to as delta) has only 16 mutations in the spike protein.
On November 27, 2021, the scientific research team of the Children's Hospital of Rome in Italy released the world's first picture of Omicron, comparing the spike proteins of Delta and Omicron, indicating that Omicron has more than Delta. Spike protein mutation. Mutations in Omicron are diverse, mostly in the region that interacts with human cells, the receptor-binding region (RBD). Omicron has 10 RBD mutation sites, 3 beta variants, and 2 deltas that are still raging around the world.
Because of these mutations, some professionals believe that the overall risk of Omicron is relatively high, and may have characteristics such as "high contagion" and "effectively evading the body's immunity." Although Omicron has far more spike protein mutations than delta, the amount of mutations in the virus as a whole is not large. The genome of the new coronavirus has 29,903 bases. Compared with the standard strain, Omicron has only mutated more than 30 bases. Compared with all the bases of the new coronavirus, this amount of mutation is still very small.
At present, researchers cannot confirm the origin of Omicron. Although Omicron was first detected in South Africa, researchers in Botswana and Hong Kong have also publicly released the genetic sequence of Omicron. The most likely situation is that this variant strain first appeared in southern Africa, and the gene sequencing networks in South Africa and Botswana were relatively developed, and the virus was first discovered. Omicron may have appeared in other countries as well, just not being detected.
Immune escape and toxicity
Immune escape refers to the ability of a virus to escape the attack of the human immune system. The ability of the human immune system to fight pathogenic microorganisms can be divided into two parts, one is the immune response and ability of the human body caused by the natural infection of the pathogen; the other is the immunity generated by the body after the injection of the vaccine.
Previous studies have shown that K417N, E484A or N501Y mutations appear in the S protein of the new coronavirus, suggesting that its immune evasion ability is enhanced. Now, Omicron also has a triple mutation of "K417N+E484A+N501Y", and the N501Y mutation will make the viral S protein bind more strongly to the ACE2 receptor in human cells. Omicron also has multiple mutations that may reduce the neutralizing activity of some mAbs. From these circumstances, Omicron may reduce the protection of existing vaccines, and may also reduce the resistance of some antibody drugs.
The results of the Omicron serology study, published on December 8, 2021, by a research team at the African Health Research Institute in Durban, South Africa, provide some real-world evidence. The mutant strain can partially escape the protection provided by the Pfizer mRNA vaccine, but people who have been infected with the new coronavirus and have been vaccinated may be well protected.
South African researchers tested serum samples from 12 volunteers who had all completed the Pfizer vaccination. The test results showed that Omicron could partially evade the immune protection established by the vaccine. Compared with the original strain of the new crown virus, Omicron can significantly reduce the immune neutralization effect stimulated by the Pfizer vaccine. The researchers also tested using human lung cells. The study found that the neutralizing activity of these sera to the early strain D614G FRNT50 (serum antibody titer that can neutralize 50% of the viral load, i.e. the dilution factor) was 1321, and that of the Omicron mutant was 32, a significant decrease. big. However, the study has not been peer-reviewed.
The study also showed that Omicron did not appear to increase the risk of primary infection, but simply made re-infection more likely. In addition, the sera of 6 volunteers who were infected with the new coronavirus and then vaccinated were able to better neutralize the virus, indicating that vaccination after infection with Omicron has a better protective effect.
The clinical situation also shows that Omicron may not be the most virulent or virulent. The South African doctor and director of the South African Medical Association, Angelie Coetzee, who first warned about Omicron's emergence, said the symptoms of cases infected with the strain were "unusual, but mild." A typical symptom in patients infected with Omicron is "extreme fatigue," but no loss of taste or smell. Patients with mild symptoms may experience muscle aches, fatigue, and discomfort for about a day or two. It can be seen that the pathogenicity of Omicron is not very strong. However, Coetzee noted that most of the more than 20 patients she has treated with Omicron's disease were healthy men, and half of the confirmed cases had not been vaccinated. This means that people who are vaccinated will also be infected with Omicron, and at the same time, Omicron also has the ability to immune evasion.
A report published by the scientific journal "Nature" pointed out that scientists in South Africa found breakthrough cases of Omicron in Pfizer, AstraZeneca and Johnson & Johnson vaccines respectively, which also proved that Omicron does have immune escape. ability. Shub, chairman of the South African government's new crown pneumonia committee, also pointed out that South Africa has a large number of Omicron breakthrough cases, and fully vaccinated people have also been infected, but so far, the symptoms are mild. To judge whether Omicron is more pathogenic, it also needs to see whether it causes more people to be infected in a short period of time. Although South Africa currently has more cases of Omicron (the exact number is yet to be counted), preliminary data suggests that the increase in hospitalizations in South Africa may be due to an increase in the overall number of infections, rather than specific infections in Omicron. To. As a result, the World Health Organization said it was unclear whether Omicron was more contagious than other variants of the new coronavirus and could cause more severe disease.
Hypotheses and models about Omicron
In addition to the above conclusions based on existing scientific research and investigations, there are also inferences and hypotheses based on mathematical models or other factors.
The latest hypothesis on the contagiousness of Omicron comes from research at Nankai University in China. Through big data modeling analysis, the team of Huang Senzhong from Nankai University found that the infectivity of Omicron is about 37.5% higher than that of Delta. They intercepted the daily newly confirmed data in South Africa from October 18 to November 28, 2021, and enabled the infectious disease transmission prediction system under the assumption that the average incubation period and infectious period of Omicron and Delta were close. (EpiSIX) was fitted to draw the above conclusions. However, this is only a mathematical model, not based on actual statistics of clinical and confirmed cases. Therefore, in the future, more accurate conclusions can only be obtained based on the statistical results of the actual infectivity, the number of patients and the pathogenicity of Omicron, and compared with other mutant strains.
Why did Omicron evolve more mutations? The World Health Organization and China's National Health Commission also gave answers, but there are also some speculations and hypotheses. There are roughly three reasons for the more mutations in the Omicron gene: after immunocompromised patients are infected with the new coronavirus, the virus has undergone a long period of evolution in the body and accumulated a large number of mutations, which are spread by chance; a certain group of animals is infected with the new coronavirus , the virus undergoes adaptive evolution during the spread of animal groups, and the mutation rate is higher than that of humans, and then spills over and infects humans; this variant strain has been circulating for a long time in countries or regions where the monitoring of new coronavirus genome variation is backward, due to insufficient monitoring capabilities. , the evolution of the intermediate generation of the virus has not been discovered in time.
In addition, there is an inference recognized by international mainstream scientists for the appearance of Omicron, that is, it is related to AIDS patients and evolved from AIDS patients. However, Omicron is not directly related to HIV, such as a genetic jump, or a combination of the two, but refers to the fact that HIV-infected or AIDS patients are infected with the new coronavirus due to their low immunity. , Autoimmunity is not enough to curb the replication and mutation of the new coronavirus, thus providing a fertile ground for the new coronavirus, and finally producing a mutant strain of Omicron with more mutations.
Whether Omicron was first produced in South Africa or Botswana requires research to confirm. At present, researchers believe that, based on the more than 8.2 million people living with HIV and AIDS in South Africa, Omicron is likely to complete the mutation process in untreated AIDS patients. It is highly likely that Omicron's mutation came from a single infected person, and this patient is likely to experience the worst outcomes after infection, because the consequences of two viral infections are far greater than one.
After people are infected with HIV or AIDS, their immunity will gradually decrease, because HIV specifically attacks and replicates in T cells that play a role in immunity. Due to the low immunity of AIDS patients infected with the new coronavirus, the new coronavirus can evolve and replicate in large numbers in the human body. In this process, the proportion of new coronavirus replication errors is higher, and due to the persistence of the virus, various mutations that have been generated may be retained and gradually accumulated, eventually forming an Omicron containing a large number of mutations.
From this point of view, if advanced AIDS patients with extremely low immunity in the future are infected with the new coronavirus, it is possible to produce more and more mutated new coronavirus mutants. Therefore, AIDS patients may become a new source of new coronavirus mutations. However, whether AIDS patients will produce a more virulent variant of the new coronavirus remains to be confirmed by future studies.
A hypothesis can also be drawn from this inference. If AIDS patients are infected with the new coronavirus in the future, resulting in the production of more new coronavirus variants in their bodies, these variants may also develop towards a weakened pathogenicity. Because AIDS patients have low immunity and weak ability to resist the virus, the new coronavirus will mutate in a random and natural way, rather than evolving in a specific direction. In contrast, antibiotics are widely used today to treat infections and other diseases, and bacteria will purposefully evolve against antibiotics to evolve into antibiotic-resistant superbugs, such as methicillin-resistant Staphylococcus aureus, Vancomycin-resistant enterococci.
realistic prevention measures
Whether it is the World Health Organization or the National Health and Medical Commission, the attitude towards Omicron is "important, but don't worry, let alone panic." International and domestic plans have been prepared for a long time, and in the past two years, rich experience, technologies and methods have been accumulated in anti-epidemic.
First, the current detection method is valid for Omicron. The Institute of Virology of the Chinese Center for Disease Control and Prevention has established a specific nucleic acid detection method for Omicron, and continues to carry out virus genome surveillance for possible imported cases. This is conducive to the timely detection of Omicron cases that may be imported into my country. Since Omicron has a gene target of the S protein missing, nucleic acid testing can quickly detect Omicron.
In addition, after the emergence of Omicron, the World Health Organization recommended that governments strengthen the monitoring, reporting and research of the new coronavirus, and take effective public health measures to block the spread of the virus. The government should ensure that the early warning system is in place and can effectively provide the public with information. The government should promptly, openly, and transparently inform the public on a regular basis about Omicron and other people infected with the virus and the potential impact on the public. In the future, the number of people infected with the new coronavirus may increase, which will put pressure on health systems, and governments should develop plans to prepare for potential threats.
The World Health Organization also recommends that individuals take effective infection prevention measures, including keeping a distance of at least 1 meter in public places, wearing masks, opening windows for ventilation, keeping hands clean, coughing or sneezing into the elbow or tissue, vaccination, etc., and avoiding Go to poorly ventilated or crowded places.
What is currently known is that all new coronavirus variants have the potential to cause severe illness or death, so preventing the spread of the virus is always the key, and vaccination against the new crown is still effective in reducing severe illness and death. However, in the case of completing the whole course of vaccination and vaccination booster, it is also necessary to wear masks in indoor public places, public transportation and other places. In addition, personal health monitoring should be done well. When there are suspected symptoms of new coronary pneumonia, such as fever, cough, shortness of breath and other symptoms, timely monitor the body temperature and take the initiative to seek medical treatment. Reducing travel and non-essential entry and exit can also reduce the risk of contracting variants such as Omicron and Delta. Travel to high-risk areas should be minimized, and personal protection during travel should be enhanced.
In addition, preliminary evidence shows that people who have previously been infected with the new coronavirus may also be re-infected with Omicron, so vaccination is still crucial to reducing the probability of severe illness and death. In terms of treatment, cortisol and interleukin 6 (IL6) receptor blockers are still effective in the treatment of patients with severe new coronavirus infection. Of course, researchers in the field of clinical treatment need to further evaluate the treatment methods and treatment effects for people infected with Omicron.
