Unveiling Omicron: Will it be the last coronavirus variant to wreak havoc around the world?

Written by: Zhu Hengheng

Editor: Wang Haha

Layout: Li Xuewei

In the past 2021, the global COVID-19 situation is still not optimistic. The Delta strain continues to ravage the world, and the cumulative number of confirmed cases continues to surge, exceeding 300 million to date, and the death toll has already exceeded 5 million. For China, which strictly implements the zero-clearing strategy, the current epidemic prevention situation is not optimistic. Small-scale epidemics have broken out in many provinces and cities across the country. The number of new cases in Shaanxi once exceeded three digits per day, and Henan also reached double digits.

At the beginning of 2022, the epidemic in Shaanxi and Henan had not yet ended, and Tianjin had the first batch of local cases of Omicron in my country. This round of Tianjin epidemic first occurred in two local cases diagnosed among people who actively sought medical treatment in the early morning of January 8. The whole genome sequencing of the new coronavirus confirmed that they were infected with the Omicron variant. In the subsequent large-scale screening, there were 20 new confirmed cases.

(Source: CCTV.com)

In addition, according to the latest news from the Anyang COVID-19 Prevention and Control Command Office in Henan Province, cases of infection with Omicron in Tianjin have spread to Anyang. After whole genome sequencing of the viruses of two local patients in Anyang City by the Henan Provincial Center for Disease Control and Prevention, it was found that these two patients belonged to the same transmission chain as the Tianjin epidemic.

With the approach of the Spring Festival and the holding of the Winter Olympics, the large-scale population movement in China is bound to have an impact on China's epidemic prevention and control, and the emergence of the more transmissible Omicron strain in China will undoubtedly further increase the difficulty of epidemic prevention and control. Therefore, in order to better prevent and control the new crown epidemic, we need to have a clear understanding of the Omicron variant.

1. Origin of Omicron

On November 24, 2021, South Africa reported a new coronavirus variant, B.1.1.529. On November 26, the World Health Organization held an emergency meeting, listed this new variant as a variant of concern, and named it Omicron.

Subsequently, Omicron began to spread around the world, replacing the previous Delta variant and becoming the most common new coronavirus variant in the world. Taking the United States, which has the highest number of cases in the world, as an example, since the first Omicron case was discovered on December 1, in less than three weeks by December 18, Omicron infections accounted for more than 70% of the daily new infections.

However, although the first case of Omicron infection was confirmed in South Africa, scientists still don't know when and where this variant appeared until now.

(Source: Muaz Kory/Al Jazeera)

At present, scientists have two main explanations for the origin of Omicron. The first explanation is that after a person infected with AIDS or severe immunodeficiency was infected with the new coronavirus, the virus could not be completely eliminated, so it was able to reproduce and evolve in the patient's body from generation to generation. This process was very long and may have exceeded 300 days, which eventually led to the emergence of the Omicron variant.

It is worth noting that there are currently tens of millions of people with AIDS and immunodeficiency who need to take immunosuppressive drugs around the world. Therefore, in theory, we need to better protect people with immunodeficiency, help them get vaccinated, and provide treatment to prevent the new coronavirus from further mutating.

The second explanation is that the new coronavirus is similar to the influenza virus and is a zoonotic virus. While the new coronavirus spreads among the human population, it also survives and reproduces in the intermediate host, a certain animal, and eventually evolves into an Omicron variant. We all know that avian influenza is a certain influenza virus that proliferates and evolves in animals for a long time, mutating into a variant with very strong transmission ability, which eventually ravages the world and infects countless patients.

Although the second explanation has received less attention than the first, there are studies that support the possibility of the second explanation. Of course, scientists are still not sure which explanation is more likely. But there is no doubt that compared to the first explanation, if the second explanation is true, the pressure on human beings to prevent and control the new crown epidemic will be greatly increased, and perhaps in the future it will really coexist with humans for a long time like influenza.

2. How is it different from previous coronavirus variants?

As we all know, the new coronavirus mainly uses spike proteins to infect human cells, and the immune system also eliminates the new coronavirus by identifying spike proteins. Compared with the Delta variant, the spike protein of the Omicron variant has 35 new gene mutations, and these mutations are closely related to more effective entry into cells, evading the immune system and enhancing infectivity.

Therefore, despite the emergence of many new studies, it is almost certain that the Omicron variant is 2-3 times more contagious than the Delta variant. At the same time, the ability of previously vaccinated vaccines to prevent Omicron will also be reduced. However, the vaccine can still reduce the incidence of serious complications after Omicron infection.

Taking Pfizer's vaccine as an example, previous studies have shown that two doses of the vaccine can reduce serious complications and hospitalization by 70%, but it can only provide 33% protection against infection in the laboratory. Other studies have shown that booster shots can reduce the risk of serious complications of Omicron by 75%. Another non-peer-reviewed study showed that the immunity induced by patients who had previously been infected with the new coronavirus could not protect against Omicron infection, but people who received at least one dose of the mRNA vaccine could still prevent Omicron infection.

(Source: pixabay)

This also means that although the existing vaccine system is difficult to resist the impact of Omicron, it can still prevent serious complications in high-risk groups, and active vaccination is still very necessary.

However, at this time, there is very limited data on the severity of disease following infection with Omicron compared to other variants.

Theoretically, there are two ways for the new coronavirus to enter the human body. One is by binding to the receptor protein ACE2 on the cell surface, and then another protein called TMPRSS2 cuts the spike protein, and the virus particles fuse with the cells to infect the cells. The other is that the new coronavirus binds to the ACE2 protein on the cell surface and enters the cell through endocytosis, breaks through the vesicle through tissue proteases, enters the cytoplasm, and infects the cell.

Early studies have shown that TMPRSS2 is less efficient at cutting the Omicron spike protein than other variants. Meanwhile, some preprints have shown that blocking TMPRSS2 with chemicals can inhibit the Alpha or Delta variants, but not the Omicron variant. Conversely, using chemicals to inhibit cathepsins inhibits Omicron but not the Alpha or Delta variants. Because TMPRSS2 is more common in lower respiratory tract cells, some experts believe that Omicron infection will cause less damage to the lungs than other variants.

In addition to theoretical data, some case reports from South Africa also show that the symptoms of Omicron infection are milder than those of the Delta variant. However, the severity of the disease after infection with the new coronavirus is closely related to the age of the patient. Most of the people infected with Omicron are young people, which can easily cause confusion.

Additionally, there is evidence that Omicron can cause severe dehydration by causing fever, vomiting, and diarrhea, and may exacerbate the severity of other underlying chronic conditions, such as diabetes.

Overall, there is currently no evidence that Omicron causes more severe disease, but it cannot be simply assumed to be less pathogenic.

3. Will Omicron be the last coronavirus variant to wreak havoc around the world?

According to Professor Aris Katzourakis of the University of Oxford, who focuses on viral evolution, Omicron may not be the last worrying coronavirus variant.

After all, Omicron separated from the viral spectrum very early and evolved independently. In the future, more variants that have both Omicron immune escape and strong transmission capabilities may appear, and the new variants may be more toxic than Omicron.

(Source: pixabay)

Currently, the World Health Organization is tracking two "variants of interest" and three "variants under surveillance" as well as 30 sublineages of the Delta strain.

However, some experts believe that the emergence of Omicron may be beneficial to herd immunity. After all, vaccination and natural infection have exposed millions of people to early coronavirus spike proteins and formed an immune barrier to them. The large-scale outbreak of Omicron may further enhance and expand the body's immunity, forming a stronger immune barrier, thereby reducing the threat of new variants in the future.

References:

https://www.science.org/content/article/omicron-cases-are-exploding-scientists-still-don-t-know-how-bad-wave-will-be

https://jamanetwork.com/journals/jama/fullarticle/2787065?resultClick=1

https://jamanetwork.com/journals/jama/fullarticle/2787609?resultClick=1

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