Covid-19: lessons from the past to illuminate the future

Everyone is wondering how the Covid-19 pandemic will develop. Despite major scientific advances, the evolution potential of the coronavirus remains mysterious. We have several tools to attempt predictions. First, the epidemiological models, useful and valuable, but very sensitive to multiple parameters. There is also what is known about the behavior of RNA viruses, such as the coronavirus and the influenza virus, capable of mutations, recombinations or reassortments. We can also refer to the history of pandemics that became frequent from the Renaissance, over the course of population growth and urbanization. Since the beginning of the 20th century, pandemics with respiratory transmission have been among the deadliest.

In addition to smallpox, which killed tens of millions of people until it disappeared in 1977 following a vaccination campaign, we can cite the four influenza pandemics of 1918, 1957, 1968, and 2009. The Spanish flu of 1918 was by far the most lethal with nearly 50 million deaths worldwide. Leaving the United States in March 1918, it evolved in successive waves. The first was benign (0.1% mortality), followed by a second fatal (2-4% mortality) from September to December 1918. Singularly, the virus of the first wave after a tour of the planet in six months was suddenly became very virulent all over the world synchronously and independently. Then the Spanish flu lost its virulence by becoming seasonal, as we know it today.

The emergence of new mutants could prolong the pandemic

Of course, comparing Covid-19 and the Spanish flu should be viewed with caution, as each virus has its own “evolutionary genius”. However, it is possible to hypothesize that the exacerbation of the virulence of the Spanish influenza virus is due to the emergence of a mutant under the selection pressure of the immune population during the first wave. For the current Sars-CoV2, mutations in the Spike protein appeared in the fall of 2020 independently, in particular in the United Kingdom, South Africa, Brazil and California. These mutants, especially affecting the gene for the Spike protein, are much more contagious, apparently without increasing virulence but with uncertainty as to their ability to escape the natural or vaccine-induced immune response.

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In the near future, vaccination campaigns will play a decisive role in establishing collective immunity which will severely slow the circulation of the virus, thus minimizing the risk of new mutations. But for how long ? The emergence of new mutants that may partially escape the immune system could prolong the pandemic. Several controversial hypotheses can be advanced, without anyone knowing the truth. First, the virus could become endemic, after several waves, with low seasonal mortality. Like the influenza virus, the mutations could force regular vaccinations with suitable vaccines, easier with RNA vaccines.

Another scenario, very unlikely however, but observed in the past for certain pandemics, would be the outright disappearance of the virus, as with Sars-CoV-2 in 2002. The “zero Covid-19” hypothesis based on Prolonged confinement measures and conditional deconfinement may be possible in some countries with low population density and easy to isolate (Taiwan, New Zealand, Australia, etc.). This objective seems difficult to achieve in European countries and in America, where it is impossible to limit the multiple interactions between countries and therefore the reintroduction of new viruses. There are also cultural reasons linked to the non-acceptance of the constraints limiting public freedoms. But the history of pandemics also teaches us that they almost always end up disappearing through a balance between the virus and living beings.

For the PandemIA collective: Prof. Patrick Berche, microbiologist, Prof. Sadek Beloucif, anesthesiologist-resuscitator, Prof. Alexandre Mignon, anesthesiologist-resuscitator, Prof. Gilles Pialoux, infectious disease specialist, Prof. Vincent Maréchal, virologist, Prof. Didier Payen, anesthesiologist-resuscitator, Prof. Yvon Maday , mathematician.

The PandemIA collective will organize on March 18 and 19, in partnership with BFM and L’Express “PandemIA Days”, two days of conference on the Covid-19 epidemic, entirely online. The program and registration (free) are available on the site: https://lesjourneespandemia.fr


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