The Omicron strain may be the fastest-spreading virus in human history, but it still doesn't seem satisfied.
At present, its sub-variant BA.2 is also gradually replacing the previously popular Omicron BA.1. Compared with the earliest public perception of Omicron, the academic community estimates that the spread of the new sub-variant has increased by about 30%.
"If the Delta strain is a brute force Hulk, then Omicron is the Flash, masked and moving at lightning speed." On Feb. 11, Scientific American likened it in an explanatory report on the Omicron strain.
The article analyzes Omicron's "surprising anatomy." Wendy Barclay, a virologist at Imperial College London, said he didn't believe it would end there, and that as the coronavirus continued to spread around the world, it would come up with more ways to spread it — including one that humans hadn't even thought of.
How Omicron resisted human encirclement,
Scientific American gives the explanation
Like criminals hiding from the police, the virus also seems to be born with "wisdom", and in the course of lessons learned, it constantly tries to change the way of "committing crimes" and "fleeing" to resist the encirclement and suppression of human beings.
Citing Scientific American's latest report, Omicron's Surprising Anatomy Explains Why It Is Wildly Contagious, "more camouflaged," "more stable," "new invasion methods," and "lower toxicity" are the most notable features of Omicron, which also allows it to quickly replace Delta as the dominant strain:
More camouflage
The current academic consensus is that of all variants of the new coronavirus, Omicron's ability to evade the human immune system is unmatched.
The coronavirus spike protein receptor binding domain (RBD) binds to the human ACE2 receptor. To fight off infection, the body's immune system produces antibodies that recognize the virus's RBD, preventing it from binding to human ACE2.
But the virus is very "smart" and will change the "vest". In previous variants, individual amino acids on the RBD of the new coronavirus have mutated and "changed" to avoid the recognition of some antibodies. For example, Delta has 3 RBD mutations.
But Omicron contains up to 15 RBD mutations, many of which are located at the primary antibody binding site, which is equivalent to changing the "vest" directly to "transfiguration".
In an analysis published Jan. 25 in the journal Science, scientists demonstrated the results of this dramatic shift: Of the eight covid-19 antibody treatments currently in use, only one (based on natural antibodies) can still bind to Omicron's RBD.
There are also studies that show that whether it is vaccination or antibodies obtained by infection, mutations in RBD can allow Omicron to evade tracking smoothly.
More stable
When Omicron drastically changed the "appearance" of spike proteins, although it was not easily recognizable, it also lost some amino acid residues that are important for binding, hindering its binding to human cells.
It makes up for it using other mutational methods, and according to a recent study in the journal Science, Omicron's RBDs form new "chemical bridges" that help bind proteins efficiently.
The "chemical bridge" makes Omicron's spike protein stronger, and the subunits in it bind more tightly, avoiding the division of spike proteins before they invade human cells.
"Viruses know how to make changes appear at the right time and in the right places, trigger and enter cells, rather than before that." The researchers said.
New ways to invade
One of the most unchanging features of many new coronavirus variants in the past is that the virus relies on a protein called TMPRSS2 on the surface of human cells to help it break through human cell membranes.
But Instead of using TMPRSS2, Omicron took a completely different route into the cell. After binding to ACE2, it wraps in the vesicle structure of the cell membrane, the vesicles drift into the cell, and the virus then erupts and begins to take over the cells.
In layman's terms, "The virus did not open the lock and break the door this time, but chose to climb into the window." ”
Scientists speculate that Omicron gained two possible advantages in this way:
First, many cells don't have TMPRSS2, "and getting rid of dependence on it, viruses can infect 7 or even 10 times more cells," Wendy Barclay said.
Second, compared to the Delta variant, which often infects lung cells rich in TMPRSS2, Omicron can replicate rapidly in the respiratory tract, coughing, sneezing... It makes it easier to spread from person to person.
Lower toxicity
Unlike the first three traits, Omicron's fourth change didn't help it become more contagious. Weakened virulence, like giving up resistance, is more vulnerable to attack by the body's innate immune system.
The scientists examined The response of Omicron and Delta to interferon. Interferons act like signal flares that alert the immune system to invaders, and Delta is good at suppressing interferons — but Omicron activates them instead.
Scientists don't yet know the mechanism by which this change occurs, but the predictable results are:
The interferon response of the lungs is more pronounced than in the upper respiratory tract, and this feature of Omicron may prevent it from spreading to deeper organs, such as the lungs, thus hindering the cause of serious disease.
From the perspective of virus evolution, after obtaining high transmittal power, it reduces host mortality by sacrificing toxicity, so as to better reproduce in the human body.
Will Omicron be the last coronavirus?
Is it possible for viruses to continue to mutate and evolve? And in what direction will it go?
Let's start with one of the latest threats right now: BA.2. First discovered in India and South Africa in late December 2021, it is a sub-variant of Omicron believed to have been produced by the Omicron BA.1 mutation, a difference of about 20 mutations.
According to the latest edition of the UK Health Security Agency's research report, there is evidence that BA.2 infection has a sustained growth advantage in more than one country compared to the earliest detection of Omicron BA.1.
A preliminary study in Denmark showed that ba.2 infection in the country has largely replaced BA.1, which more than triples the susceptibility of unvaccinated people to infection compared to BA.1.
The good news is that there is currently no evidence that BA.2 is more toxic.
Virology expert Chang Rongshan told the "medical community" that BA.2 has reached a "ceiling" of virus evolution, and there is unlikely to be a stronger dominant strain in the short term. But in the long run, it will most likely not be the last mutant strain.
Professor Jin Dongyan, a professor at the School of Biomedical Sciences at the University of Hong Kong School of Medicine, analyzed that the optimistic trend is that in order to better coexist with humans, no matter how the new crown virus mutates in the future, the virulence will always be weakened or similar.
"Is it possible that both the spread and the virulence will increase?" There are, but this is a low probability event. Professor Jin Dongyan told the "medical community" that "stay vigilant, but there is no need to pay too much attention to low-probability events with limited resources." ”
There is no variation without replication, and for countries and regions that have not yet fully established the immune barrier, physical prevention and control is still one of the most effective means of epidemic prevention.
In a new paper released by the University of Hong Kong's Li Ka Shing School of Medicine, researchers say strict control measures can eliminate most of the chain of transmission, while Hong Kong's past community outbreaks have often occurred during periods when the epidemic prevention was not very strict.
Entering 2022, Japan, South Korea, Singapore, Malaysia, Hong Kong... The latest wave of outbreaks has been ushered in by Asian countries and regions.
In Europe, although with the decline in the number of confirmed cases and the establishment of immune barriers, many countries have announced the lifting of relevant epidemic prevention measures, there are still experts who are conservative or opposed.
In the above paper, HKU School of Medicine said that countries that adopted "suppression" or "mitigation" epidemic prevention strategies during the outbreak tended to spread dynamically with multiple new lineages, while our research showed that in Hong Kong, which adopted the "elimination" strategy, only two lineages formed the main virus population during the third and fourth wave epidemics.
"The idea that Omicron is the last mutant, or that we are entering the final phase of the outbreak, is a very dangerous idea." World Health Organization Director-General Tedros Adhanom Ghebreyesus recently stressed. "On the contrary, the conditions are ripe for more variants to appear globally."
Last month, The Lancet mentioned in its blockbuster forecast article that March this year will mark the end of the covid-19 pandemic. But with the number of infections still high in the world, Chang Rongshan believes that the global pandemic will not end so quickly.
"At least until August, we'll have to wait until August to draw conclusions." Chang Rongshan said.
bibliography:
1.Omicron’s Surprising Anatomy Explains Why It Is Wildly Contagious，Scientific American ，https：//www.scientificamerican.com/article/omicrons-surprising-anatomy-explains-why-it-is-wildly-contagious/
Source: Medical community