"People are my habitat": a researcher puts himself in the shoes of the coronavirus to better explain it

For months, we have only talked about him ... without ever hearing his point of view! Franck Courchamp, research director at CNRS and holder of the Axa Chair in invasion biology (Paris-Saclay University), slipped the time of an imaginary interview into the skin of this terrifying SARS-CoV-2 coronavirus the planet. Beyond the fun aspect of this "meeting", it is also a way for scientists to change our perspective on the challenges of the pandemic and the lessons that they would be happy to learn from it.


Who are you, coronavirus?

JI would start by saying, modestly, that I am the King. The king. After all, crown in Latin means "crown", so you yourself recognize it by giving me this name. I'm an evolutionary gem, yet I've kept it pretty straightforward. Paradoxically, this simplicity is a source of misunderstanding for you. You already have a hard time deciding on a point as basic as whether or not I am alive ... In your defense, you are asking yourself the same question for all my other virus colleagues.

Personally, I don't care where you rank me. It is true that my functioning differs significantly from that of living beings. You can see in me some kind of microscopic biological machine. My program is very simple: survive and reproduce myself to continue from one generation to the next. In this I have exactly the same objective as all living species.

The difference is surely that I only need the strict minimum for this: I get into my host's cells, and I borrow everything I need to function. By diverting the machinery from the cells I infect, I make copies of myself, I replicate as much as I can. My peers, brand new virus particles, are then released all around, and storm other cells. We, the coronavirus, let's produce 1000 viruses per infected cell, in just ten hours!

And yet, I am not tall. My diameter is the order of a hundred nanometers, or a ten-thousandth of a millimeter.

I am therefore a thousand times smaller than bacteria, themselves 10 to 100 times smaller than a human cell. 50 trillion times smaller than a drop of water. On my scale, your cells are much bigger to me than your cities are to you.

Why are you infecting people?

It's a strange question. People are my habitat, my ecosystem, and my resources. It is as if I were asking you why you live in this plain or on this mountain.

However, unlike you, I do not have an easy sedentary life. I am a nomad, because my ship (you, or the animals I infect) is not immortal. In order to perpetuate myself, I must therefore constantly switch to another host before the first one disappears. It must be recognized that sometimes, we have something to do with it: some of our hosts do not support our proliferation, which can tend to damage their organs. But it also happens that our guests are victims of the war waged by their immune system, that sometimes ends up out of control.

How do you infect us?

As far as I'm concerned, my means are simple and you have already unraveled some of my secrets, such as the one which consists of traveling in the droplets of postilions, of sneezing, and of staying on the hands or objects handled by people who touched their saliva or snot.

I can fit 100 billion of my congeners per milliliter in a sputum and I can hold 5 days on plastic or 7 days on a surgical mask. I am not very sophisticated, but efficient. Like all other viruses, in fact. Efficiency, that knows us, our adaptations have no limits.




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Take, for example, the major difficulty of transmission to another host. Why do you think that when you are infected you sneeze? Once contaminated, you are transformed into a powerful spray capable of transporting us at more than 50 km / h in a cloud of tens of thousands of droplets towards our new victims (or in your hands, which you then put everywhere).

Sneezing is a very effective means of spreading respiratory pathogens ...

Another example: it's not easy to move when you don't have a foot. Fortunately, you have glanders, and you make it all the more when we infect you, we respiratory viruses. No wonder: it's a very practical means of transport to transmit us more easily ... Some other viruses choose different fluids, liquefy your stools and give you diarrhea. Result: a very efficient mass transmission too… No contact with anyone? Never mind: we can lodge in your seminal fluids and pass it on to us during sexual intercourse. You can isolate yourself as much as you want, as a species, you have to go through reproduction at one time or another ...

As for viruses that change behavior to allow easier transmission, such as rabies, which disorients and makes you aggressive, ready to bite, difficult to fight against that, isn't it…

Scanning electron micrograph of a cell heavily infected with particles of the SARS-CoV-2 virus (in yellow), isolated from a sample taken from a patient.
NIAID / NIH

Why are you viruses so angry with humans?

You shouldn't be so self-centered. We don't blame you, we don't have any feelings, good or bad, towards you. You are just choice ships.

Because it must be said that as hosts, humans are perfect. They make it easier for us in many ways. Already, they often live in very dense places, and their overall population is interconnected. This gives us viruses almost systematically access to all available hosts, from one end of the planet to the other!

I have demonstrated it well in recent months: starting from any region of China, I very quickly (and without little legs), managed to invite myself to all continents, and even to the most remote corners of the world. The other animal populations are generally fragmented, which limits our potential for dispersal and limits us to small regions. We go around in circles. But with humans, it's something else! No more a sea, no more a mountain stops us. We travel from one host to another by boat, by plane: perspectives without borders, without limits! In theory, in less than a week, I can create hotbeds of infection on all continents.

In addition, you make things easier for us: human beings keep a large part of their population in rather deplorable sanitary conditions, which greatly facilitates our transmission. Not to mention the behaviors of some of your leaders, who either lack the morality or the intelligence to act responsibly. All of this creates incredible opportunities for us in certain corners of the world, where the epidemic is officially minimized so as not to have to be controlled ...

But, basically, you don't infect humans ...

Indeed, I was originally subservient to other animal species. But for all the reasons I just explained, we the viruses that infect other animals than human beings, we have reason to be jealous of those who have been able to adapt to such a host! However, by dint of copying and recopying ourselves within the cells that we infect, it happens that from time to time, one of our replicas mutates, and becomes slightly different from the others. And, from time to time, one of those mutants hits the jackpot: its mutation makes it able to survive in - and be transmitted through - animals other than those that its congeners usually infect. This new strain of virus is then ready to change host.

But this situation is very rare. All the more rare since it is not only a question of acquiring the capacity to infect a new animal species: it is still necessary to be close enough to be able to infect it! The likelihood of these events coinciding is quite slim, but two factors are at play.

On the one hand, there are many, many of us. Are you around 5000 species of mammals? We have about 320 different viruses infecting mammals! A great array of possibilities, since the more viruses there are, the more mutations there are.

On the other hand, you humans make it easier for us by increasing our contacts with other species, and therefore the chances we have of meeting you, and of coming to your home. Between all these brutal forays that you make in the fragile territories of species already stressed by hunting, the lack of habitat and resources, pollution or the climate, and all the wild species that you hunt, cage, pile on your markets, eat more or less well cooked, at a rate of millions of tons per year, the opportunities to infect you are more and more frequent. This is how the HIV, SARS,Ebola, Zika or MERS have visited you in recent years.

We can also add that when a virus does not fall on humans, but on one of its domestic species, the result is quite similar. When you nibble at the territory of bats and set up intensive pig farms at the foot of their devastated habitats, you increase the chances of a bat virus (randomly the Nipah) passes to the pig when it comes into contact with their saliva or droppings (in which viruses are present). As these pigs live in very high density and in poor sanitary conditions, the chances of transmission increase and nothing can stop us.

Imagine guests side by side, as far as the eye can see, weakened, stressed, alive in their droppings and among corpses already fallen, for a virus, it's all-you-can-eat buffet! This is how the friends of the avian flu H5N1 and swine flu took poultry and pig farms by storm a few years ago. These concentrations of unhealthy hosts lead to extraordinary concentrations of the virus. This increases our chances of moving from pets to humans afterwards. Like Nipah (which causes 40 to 75% mortality in you), or H5N1.

And as I said above, the difficulty (quite relative now) is to infect the first human. Then your globalization system does the rest. To believe that you created it all for the free circulation of viruses! So thank you very much, thank you very much, danke schöne, 衷心 感谢, muchas gracias, большое спасибо, etc.

Are you aware of the harm you are doing?

We don't want you more harm than a sheep would harm a tuft of grass. If we had the choice, obviously we would prefer that our infected humans never die and continue to shelter us indefinitely. It would make our life much easier, believe me. But their lethal nature sometimes prompts us to replicate quickly so that we can infect another human before the first one dies. This intense replication creates symptoms that are sometimes harmful or even fatal. One of the problems is that if we just sit back and keep a low profile, our low starting numbers can quickly be overwhelmed by your immune system, if we can't hide well enough in your body. Between surviving without doing too much harm and being eliminated, the balance is not easy to find!

Either way, we viruses and the species that we infect are mostly linked by hundreds of thousands of years of coevolution, so that in the end we are generally well "adapted" to each other. , with in the vast majority of cases little damage on one side or the other.

Above all, we must not forget that we viruses play an important regulatory role on the populations of other living beings (from microorganisms to plants and animals). If we all disappeared overnight, it is possible that they would end up being overcrowded, risking starvation after having increased so much that they would deplete their resources ... Moreover, it is said that we are of of major importance forecology and evolution of the living world.

Also, many viruses are good for you, for example because they kill bacteria that you don't really like either. Some are even considering use them to supplement antibiotics!. Also, let's not forget that viruses can have an effect that could be described as “neutral”. In humans, always, since that's what interests you, there are around 5000 different viruses, but less than 3% of them cause disease, in other words are "pathogenic". It's not really that much ...

Finally, there are all the viruses that care so little about you that you don't care either. Present in the ground, in suspension in the air, floating in water, they infect plants, insects or starfish… For example, we find a million viruses suspended in a liter of sea water. In fact, there are so many viruses in suspension in the oceans that, put end to end and despite their ridiculously tiny size, the length obtained would represent a distance exceeding the neighboring galaxies of ours.

Again, viruses are everywhere, even if you can't see them… And sometimes they're right in front of your eyes, and you don't recognize them, like these extraordinary giant viruses, bigger than some bacteria, with which we initially confused them...

Besides, where are you viruses from?

I imagine you mean when are we from? In fact, we've always been there. In any case since humans have existed, and even long before your first animal ancestors. Some say we are older than the oldest bacteria.

Already present at the origin of life, we have played an essential role in evolution, in particular by allowing gene transfers not from one generation to another, but indeed between species. We are so old that some of us have integrated into your genomes here and there, and finally become an integral part of you.

In total, not far from 10% of your genome is virus DNA assimilated into your chromosomes. And of all these new genes that we've brought you, some are important, even essential. In mammals, for example, the embryo is accepted by the mother's immune system despite its foreign character (it is a hybrid between the father and the mother), only by the existence of the placenta, whose origin is due to a virus embedded in your genome. So, thanks who?

And yourself, where are you from, SARS-CoV-2 coronavirus?

What species did my ancestors infect before coming to you? I do not know. But bat, pangolin, monkey, or whatever? What would you do if you found out? Would you stop poaching and devouring this species? Would you exterminate him? Would you do the same for all the species from which you were at risk of catching viruses? Obviously impossible, it would be practically all animals ...

And why are you looking for culprits when they are all pointed out? Rather, are the culprits not those who “seek out” viruses by disrupting relatively hermetic virus-animal systems for millions of years? If you get scratched by a cat that you annoy, are you going to eliminate all cats? Shouldn't you instead learn to stop pulling their tails?

How do you get rid of you?

In theory it is quite simple. It is enough to think of epidemics as forest fires. Both are natural phenomena, but when you play with the laws of nature they can get out of hand.

Fires are, for example, favored by an accumulation of favorable conditions (such as dead wood piling up). After a rapid outbreak, they usually disappear: either because they arrive in areas where the trees are too far apart for the flames to pass from one to the other (the equivalent of your social distancing), or because 'they arrive in areas where tree species are less flammable (they are immune to fire).

In the case of natural epidemics, the situation is relatively similar. They emerge and then spread until the contagion is halted because most of the infected fail to infect other people. This may be due to the fact that they no longer meet them (because of the implementation of social distancing measures, quarantine, etc.), or because those they meet are immune (immunity acquired during a past infection, or through vaccination). If the rate of infections decreases, then the epidemic subsides, until it disappears.

The important question is therefore rather how not to catch the next of your fellow viruses?

Indeed, because it is not a question of knowing "if" a new virus dangerous for the human being will emerge from another species, but "when".

Will you be ready? Better to be able to respond quickly, because epidemics from wild animals multiply in recent years, and your companies have already tasted my virus cousins ​​on several continents ...

We emerging viruses have killed millions of yours, sometimes hitting your fellows at random, or attacking very targeted categories (like here the most physically vulnerable). We have damaged your economic and political systems, we have locked you in your home, terrorized, gives rise to conspiracy theories the most absurd… What did you remember?

And you, what do you have in store for us in the future?

I would be hard pressed to tell you: me and my prolific offspring we go at random infections and mutations.

If you survive my passage through your body, will you be immune to my return, once healed? I don't know, and that's not my problem. Will you be able to keep me at bay with masks and physical distancing during the second winter wave? We will find out together.

One thing is certain: I will not remain absolutely identical from one year to the next. Remember, we viruses are mutating. And if there are so many of us - like, say, when millions of humans are infected, which we are now - then there are more of those mutations too.




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Among them, most mutations result in strains that are less viable, less contagious or less virulent. These will disappear quickly. More rarely, mutations result in more contagious or deadly strains. Even if these more dangerous mutations are less frequent in coronaviruses, the more difficult it is to keep us in check, the more of us there are, and therefore mathematically the more you increase the chances of a more dangerous strain appearing ...

Rest assured, however: a virus that becomes so dangerous that it completely destroys its host population, that does not exist. Quite simply because it would simultaneously destroy its resources, its ecosystem and its environment. It would therefore disappear at the same time. And even though I'm not smart, I'm not dumb enough to destroy my own environment. Who would be?

Frank Courchamp, CNRS Research Director, Paris-Saclay University

This article is republished from The Conversation under Creative Commons license. Read theoriginal article.

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