Our lives were turned upside down for several months with the advent of the new coronavirus, SARS-CoV-2. At the time of writing, there is a pandemic According to the WHO, The World Health Organization, has killed more than 1.4 million people and infected more than 61 million people worldwide. In Belgium, a few days ago the death toll exceeded 16,000.
We now know that 80% of cases of Covid-19 will not develop a severe form of the disease, although it can last and be more painful than the flu, they will stay at home. For the rest, 10 to 15% of infected people will have to be hospitalized and need oxygen. Extreme cases remain, less than 5%. These severe cases will be hospitalized in intensive care, intubated and need ventilator assistance.
For months, studies on SARS-KOV-2 have followed each other to better understand this new virus. In this article, we review the state of knowledge, but also the uncertainties about this virus.
Come back here
If SARS-CoV-2 probably appeared before December 30, only on that date was it reported globally through a network specializing in this type of warning. The content of the message read: pneumonia of unknown cause. The possibility of viral pneumonia has already been mentioned. Let’s go back …
Very early on, the genetic sequence of the virus was available. This allowed us to make comparisons with viruses we already knew and classify them as coronaviruses. Therefore, we quickly realized that this newcomer is close to SARS-CoV, discovered in southeast China in November 2002 and infected more than 8,000 people a few months later, 800 of whom died.
The knowledge produced on SARS-CoV was initially used as a reference for the virus that occupied us for several months, namely SARS-CoV-2 and Covid-19 disease. Emanuel Andre, microbiologist: “for example, how does the virus communicate with the human body, through which receptors? Very quickly, like SARS, it was suggested that these known ACE2 receptors were the entry point into human cells for this new virus.“
Over time, new knowledge has shown that there are still subtle differences. Until recently, a team of scientists in Bristol discovered that this new coronavirus could also bind to a second receptor, Neuropilin-1. This causes SARS-CoV-2 not only to develop differently but also to cause slightly different pathology.
“True discoveries took time, but because we were able to study previous viruses and the like, we were able to move forward relatively quickly.“, comments the microbiologist. These years”of peace“As he says, between new viruses, let them be studied and then let them, based on similarities, suggest lead (vaccines, antivirals, etc.) when a new virus arrives.”
The peculiarity of SARS-CoV-2
Therefore, there are differences between these viruses. For Emanuel Andre, the most important difference and what allowed the virus to enter the human species is that, without forgetting the serious forms of the disease that we face every day in hospitals, in most cases it causes little or no symptoms. This feature allows the virus to spread rapidly and rapidly in the population.
Besides, to make matters worse, infected people can infect others before the first symptoms appear and therefore continue their social life without realizing that they are contaminating other citizens. “That, if we put ourselves in the place of a virus, it is a very important advantage to be able to spread quickly“
If we compare, for example, the current SARS-CoV-2 with MERS-CoV, another coronavirus, the latter has a higher mortality that requires us to take precautions, protect ourselves, treat ourselves and therefore avoid contact with others. For the virus, this feature is a disadvantage.
Did the virus mutate?
Above all, viruses want to multiply. But these copies are not perfect, there are always defects in their genome. In contrast, human cells have a control system that allows them to check if the copy is identical, which protects us, for example, from premature aging or from forms of cancer.
“Viruses that have a much smaller genome and protein arsenal are unable to do this screening.“, Emmanuel Andre tells us. “And so, they make a copy, if it works, the better, if it does not work, the virus is not sustainable and it does not matter, there will be more …“
Conclusion, because viruses tolerate imperfect copies, there will naturally be accumulations of mutations in the genome. Some mutations sometimes go unnoticed, the virus will either die or the change will have no effect.
The question behind these genetic mutations in the virus is whether they can ultimately reduce the effectiveness of different vaccines. Since the virus is no longer the same, will the vaccine still be effective? For Emanuel Andre, the question is legitimate, but he says: “what you need to know is that the virus does not have much opportunity to modify. If it changes too much, it will no longer be sustainable […] the vast majority of mutations will mean that he will lose more in virulence and will therefore be at a disadvantage“
Theoretically, a mutation that would make the virus more pathogenic is always possible, but continues with the microbiologist: “this is probably what happened before the virus reached humans. At that time he had mutations that were useful to him to infect humans, but now that he is very well in his environment, there is little chance that mutants will develop and be pathogenic to him. humanity“
At this stage, current mutants do not appear to have a sensitivity that varies with the immunity developed by the vaccine. The risk of mutation of the virus and making the vaccine less effective still exists, even if it is minimal. This includes setting up a system to track the evolution of genomes around the world in order to prevent such a scenario. This does not include an overview of everything, but the vaccine needs to be adapted.
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Finally, remember that the more we let the virus circulate and multiply significantly, the greater the risk of finding a mutation that is in its favor. For Emanuel Andre: “It is not because we have a vaccine in the future that letting the virus circulate becomes a more acceptable strategy “
Keep in mind that the flu virus we know better is a little special and that it can mutate and change every year. This explains why the vaccine varies from year to year.
We talked a lot about it after the first blockade. Is SARS CoV-2 a seasonal virus? We can see that there are seasonal peaks. “The virus arrived at our home in the winter and when the sunny days arrived, despite the fact that we were a little less careful, it took some time to restart“And indeed at the end of the summer, the epidemic continued with more energy in Europe.”It’s not a virus that we will see as pure / inclusive as some viruses that we do not see in the summer, but there is a seasonal trend that seems to be emerging“
The second part of this article, Covid-19 disease, will be published this week, December 6, 2020: Coronavirus: almost a year, what we know about Covid-19 disease