According to the definition of the Spanish Royal Academy, “trompe l’oeil” is a trick or illusion with which someone is tricked into making them see what they are not.

One of the few gratifying aspects of this crisis is finding scientific interest and language in all kinds of settings, some unexpected.

When I overheard a waitress speak to a customer about her PCR while serving coffee with churros a couple of days ago, I thought something had changed in our society, perhaps forever.

Hopefully the knowledge that we are spreading and acquiring to forced marches in this sedimentary pandemic and become transferable to normal situations.

Hopefully it is not disposable, like those millions of masks that now grow landfills.

The different stages that this crisis is going through They continue to raise new questions for the experts, whose answers are then commented or discussed by the population with visible interest.

Weeks ago we passed the moment of understanding the reproductive rate, seroprevalence or the difference between a PCR that detects infection and an immunological test that detects if we have passed COVID-19.

The big concern at the moment is whether the virus has become less virulent.

Rigorous results take time to arrive

Unfortunately, science takes much longer to respond than the horoscope.

It needs time because it does so with a need for rigor that we are not used to in these times when opinion tries to take away the place of knowledge.

Coronavirus labeled pipetteDo you know what the difference is between a PCR test and an antibody test? THE PRESS / .

Scientists cannot yet give a forceful answer on whether the virus has lost virulence or not, because they need to apply an elaborate method and be certain before making emphatic claims.

That is the reason why rigorous results are expected. And nobody should be angry because thanks to that, for example, they can put anesthesia on us when we go to the dentist.

However, one thing scientists can do now is explain what the dynamics of other viruses have been like in comparable situations.

Data from the past teaches us that it is true that viruses, after reaching a new host in a fury, become less aggressive over time. So it is expected that it will happen again in this pandemic. But it can still take time, and may never happen.

An important detail to keep in mind when talking about virulence is that, although we usually talk about viruses in the singular, in reality what infects us are hundreds or thousands of viral particles (or virions) simultaneously.

Dexamethasone is a cheap and easy to get medicine. THE PRESS / .

When they infect us, they tirelessly repeat the same process: one or more of them enter a cell and produce hundreds or thousands of new viral particles. In other words, a characteristic of viruses is their simultaneous abundance of copies. They are small, but many.

So, if the current coronavirus is about to lose virulence, it needs to be lost by the billions of virions that infect the millions of individuals of our species.

And of course, that doesn’t happen overnight. The process is not easy: it is not that a certain viral particle decides to moderate its attitude, as if it were a person who feels the head and intends to stop going out on the spree during the week to get married and have children.

Random errors

For a virus to lose aggressiveness, mutations must accumulate in the genetic material (RNA) of the new virions that are emerging.

Those mutations are molecular modifications that occur randomly in that instruction manual for each viral particle that is your RNA.

These changes can produce new virions that carry RNA that makes them less aggressive. Although being random, mutations can just as easily generate more virulent virions or have no effect.

Plasma transfusions offer hope for covid-19 patients. THE PRESS / .

Each SARS-CoV-2 viral particle that enters one of our cells produces many new copies. In them there will be a great majority that will be exact, and only a few mutants.

This is normal when many copies of genetic material are made: the machinery usually does its job well, but sometimes it becomes confused and makes mistakes. It would happen to anyone if they manually copied a text thousands of times.

The less virulent you have more options to survive

It is key to understand that these random mutations are not necessarily making the new virions less aggressive, but simply different.

However, after a certain time it is probable to observe that the less aggressive viral particles are becoming more abundant, displacing the most virulent ones. In the same way that the most attractive products are displacing the old-fashioned ones in the shop windows.

Why this replacement? What is the criterion that “makes fashionable” the least aggressive virions and makes the most radical obsolete?

There is no window dressing making decisions, it is simply a well known evolutionary phenomenon, natural selection. The version that manages to spread better will leave more copies of itself.

If new, less aggressive virions enter an individual and allow him to lead a normal life with greater comfort than if more virulent had invaded him, they will be more easily transmitted by this carrier.

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An infected by these more “bearable” mutants will make a life more contagious than if he were feverishly bedridden or isolated in a hospital ward. The most moderate virus is prevailing in the population with an infallible strategy: let its bearer go to parties or conferences.

Thus, little by little, the less aggressive viral particles become more frequent, which adapt to coexistence with their habitat, that is, us.

When a virus reaches a species for the first time, it can show different degrees of virulence towards its host, but if it manages to perpetuate itself, it is because it ends up showing a tendency to reach a coexistence balance.

If the virus adapts to our life and let us go on the subway quietly and go out with our friends, it will be a better survivor than if it eliminates us.

The process is an example of natural selection in a small world in which the viral particles are the individuals and our bodies the environment to which they adapt.

Deceptive viral illusions

Can we then say that SARS-CoV2 is already less aggressive?

Answering such a complex question rigorously is not possible without first analyzing numerous data. It is true that we see fewer cases each time, that the patients received by hospitals are milder, that with each passing day the figures are more encouraging … pBut you probably haven’t lost aggressiveness.

Sometimes, sitting on a train about to depart, we observe the car of another convoy on the attached track.

Two female doctors in a vaccine laboratory at the Federal University of Minas GeraisTwo female doctors in a vaccine laboratory at the Federal University of Minas Gerais
Various vaccines are being developed in different countries. THE PRESS / .

After a while, we see how the neighboring car moves and it takes time to discern if it is the other train or ours that has started.

It is an optical illusion.

Probably, The lower severity and number of cases of COVID-19 that we currently observe is a consequence of past confinement, current social distancing, and the experience and capacity of our health system to attend to milder cases., among other efforts.

Surely it is not that the virus is now less aggressive, but that we are more vigilant.

It is our train that has started to move and not the one next door. But we have to be cautious and patient to avoid falling into viral illusions.

* Miguel Pita is a doctor in Genetics and Cell Biology from the Autonomous University of Madrid (Spain)

This article was originally published in The Conversation and is reproduced here under the Creative Commons license. Click here to read the article in its original version.

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