After Covid-19, the era of pandemics? “There is a list of suspects that we are monitoring” – L’Express

In December 2019, a new disease entered the history books. The Sars-CoV-2 virus, discovered in China, in the city of Wuhan, has caused more than 7 million officially recorded deaths, according to the World Health Organization – but the toll would actually exceed the 25 million attributable deaths to the pandemic across the world. Does this crisis, which has shaken the entire planet and will have visible effects for a long time to come, mark the entry of humanity into a new pandemic era? The rate of emergences (appearances of new diseases for human populations) has quadrupled in fifty years, with more than 330 episodes recorded between 1940 and 2004. Among these emerging diseases, more than 60% are zoonoses, i.e. i.e. diseases caused by animal pathogens that are transmitted to humans. And almost three quarters of these zoonoses come from wildlife.

Based on this observation, scientists decided to trace in the work The era of epidemics: Covid, research advances (CNRS-Le Cherche-Midi), published Thursday February 22, “the natural history” of Covid-19. This very in-depth book, which brings together texts from numerous French researchers, takes stock of advances in research on Covid-19 and the virus that causes this disease, Sars-CoV-2. Because Florence Débarre, CNRS research director in evolutionary biology and modeling, who coordinated this body of knowledge, indicates, like her colleagues, that this pandemic is not the last we will experience. Coronaviruses are a striking illustration of this insofar as, among the seven which currently infect humans, four, generally benign but capable of causing pneumonia in subjects at risk, are said to have emerged between the 13th and 19th centuries, and the last three , including Sars-CoV-2, in the 21st century. Interview.

You have directed a collaborative scientific work which amounts to a sum of our knowledge on viruses, and more precisely Covid-19. Why did you publish such a work?

Florence Débarre We wanted to make a book that talks about science around the Covid-19 pandemic because there have been numerous publications on the medical aspects, but much less on the scientific aspects, particularly biological ones. One of the goals of this work is therefore to fill this gap and to recall that the pandemic has also been the subject of several developments in biology. The idea was therefore to provide an overview of what we had learned about the Sars-CoV-2 virus.

How does Covid-19 mark a turning point in the history of pandemics? Because the emergence of a new epidemic is not, in itself, new…

The Covid-19 pandemic is indeed not the first to affect humanity, but it is the most recent; it had a major impact on the entire planet and turned our lives upside down. And all this because of a new virus, Sars-CoV-2! After what we have just experienced, we may want to understand how the emergence of a new disease can take place, how the pathogen replicates, is transmitted between humans, how to fight against it… and that is what that the book proposes to explain, by taking stock of the state of knowledge.

In this book, we do not find a chapter exclusively devoted to the origin of Covid-19. Why this choice ?

When defining the outline of the book, I decided early on not to specifically address this issue in a separate text from the rest, for several reasons. First, even if all the elements point towards a zoonosis at the moment, the question remains controversial. Above all, this point deserves much more than just a few pages, in particular to explain why this subject still remains debated even though the available data is quite clear. There was also a risk that it would take precedence over the rest. Nevertheless, the question of emergence is addressed in several texts, because each author had the freedom to write on the theme he had to deal with.

Furthermore, if we had done, for example, a chapter on the hypothesis of a zoonosis, then another on that of a laboratory accident, this would have given the impression that the two hypotheses are equal. However, given the current state of knowledge, this is not the case. This is not a book on the question of origins, but a much more general collective work on viruses and the Covid-19 pandemic.

To stay on the mystery of origins, it is written in the book that our knowledge, since the beginning of 2020, has evolved little on this mystery. What do we know precisely and with certainty about the appearance of this virus?

We know that the first cases were detected in connection with the Huanan market, in the city of Wuhan, China. In this place wild animals were sold, and retrospective analyzes of cases showed that the first infected and detected people resided around this market. Furthermore, in the genome of the virus, there are no obvious traces of genetic manipulation, and the virus is not similar to viruses that were already manipulated in the laboratory. Finally, we know that the closest known viruses are detected in bats, but we also find related viruses in other species, such as the pangolin for example. But we don’t have the full range of animals that are infected.

In your opinion, will we one day know the end of the story?

It is likely that the first known cases are not the very first infections, and we do not know exactly what happened in the weeks preceding the first detected cases. According to the genetic diversity observed, the start of the pandemic took place around the end of November 2019, while the first patients presenting symptoms were identified at the end of December. There have been retrospective analyzes which have identified other people who fell ill during the month of December 2019, but gaps remain. And if the data was not collected at the time – mainly because we did not know the very existence of the disease – this piece of history is probably lost forever. Afterwards, does that mean that we will never have the original answer? Not necessarily. There are other ways to get there and we know that there is still some data that exists and that remains to be shared. So there are still things to learn or consolidate. Afterwards, let’s be clear, even if we arrive at a definitive conclusion for some, it will not be so for others, for whom there will always remain the shadow of suspicion.

You talk about the advent of an “age of pandemics” in the 21st century. Have we observed an increase in pandemics in recent years? Will this get worse?

The texts of the book which address this subject note an increase in the number of epidemics, due in particular to the globalization of trade, demographic growth, changes in land use which can give rise to an increase in contact between animals. and humans. There are also the effects of climate change, and in particular the movement of the distribution areas of animals vectors of certain diseases. We therefore expect a growing impact of infectious diseases in the near future and we must prepare for it now.

How can we prepare for future pandemics?

We can prepare by considering human health as part of a whole, being linked to animal health and more broadly to the health of ecosystems, which is highlighted by the concept of “One Health”, developed at the end of the book. There is also in this work a text devoted to the possibility of emergence of diseases linked to research activities, and therefore proposing the increase of safety conditions in the laboratory.

Did the Sars-CoV-2 virus surprise the scientific community when it appeared?

It all depends on where you stand! The fact that a pandemic is caused by a new Sars-type coronavirus [NDLR : syndrome respiratoire aigu sévère] was not, in itself, a surprise. It was even a scenario considered. On the other hand, when it appeared, this virus had characteristics that we did not know. The state of knowledge before its discovery did not allow us to imagine that this virus could have had such “success”. Furthermore, it is the first known Sars-type coronavirus with a furin cleavage site. [NDLR : qui lui permet de pénétrer plus aisément les cellules de son hôte], but other coronaviruses have them. Once again, it all depends on the scale considered.

And was the appearance of numerous variants, at a fairly high speed, a surprise?

We expected there to be changes, but we didn’t know what exactly would happen. For example, one of the key mutations present in the first variants had been identified in experiments published in the summer of 2020. So when we observed it for the first time, we were certainly surprised to see that this special position in the genome had mutated, but in retrospect we knew it could happen. We can’t predict which way things will go, but there are things we can interpret.

What could the next pandemic look like?

We don’t know, but there is a list of suspects: another coronavirus or a flu virus in particular. But it could also be something else entirely. This is why there is surveillance. The idea is that if there is a surprise, it should have as few harmful effects as possible. In the enthusiasm for medical progress in the 20th century, some predicted the end of pandemics at the time, but this judgment has since been revised! Covid-19 is not the last pandemic that humanity will experience.

What are the scenarios for the continuation of Covid?

A priori, this virus is here to stay. Afterwards, we can ask ourselves the question of knowing in which direction the variants will go in the coming years. We don’t talk about it much anymore, but the virus continues to circulate, infect people and evolve. Recently, we have observed a large replacement of one variant by another. The viruses currently circulating in France, for example, have little to do with those circulating last June. BA.2.86, which appeared on radar last summer and is now dominant, is a descendant of BA.2, one of the first in the Omicron family, which circulated in early 2022. It is suspected that the The appearance of such variants is linked to chronic infections, that is to say people who are infected and who remain infected for a very long time. This gives the virus the opportunity to evolve within these people, to become very different. It is assumed that most of the time viruses adapt to the intra-human environment and do not go further, but in some cases this creates new variants that can be transmitted. And this is probably the case with the one currently circulating in France.

Conclusion: as long as it circulates, the virus continues to evolve. Until then, we are “lucky” because these are still variants of the Omicron family, which do not cause too severe infections in general. But we are never safe from a new variant whose characteristics would change more significantly. There is always this element of uncertainty. We also wondered for a while about the re-emergence of old variants, especially via these long-term infections. With the appearance of a super-modified Delta for example. The more time passes, the less plausible this becomes, but it remains a possibility. All this involves maintaining genomic surveillance to know what viruses are circulating, particularly with the aim of updating vaccines. This is a new reality.