Pandemic, year 2: the origins of the health crisis, the thesis of animal contamination seems to be more and more confirmed. A prospect no less worrying than that of a laboratory leak, and this, because of the many other epidemics that this virus discovered in nature now portends for the future. Second text in a series of two.
From uncertainties to reversals. The possible origin of the COVID-19 pandemic was moved once again a few days ago with the publication in the scientific journal Science of a new study that seriously questions the very identity of patient zero, established more than a year ago by the World Health Organization (WHO).
The international health agency said in a report that a 41-year-old man who frequented the now famous animal market in Wuhan, China, but not directly related to the location, was the first carrier of the coronavirus, which has spread. then spread across the globe.
However, for Michael Worobey, virologist and head of the Department of Ecology and Evolutionary Biology at the University of Arizona, the first contamination would have rather struck a seafood seller working in this market and was detected five days earlier. .
The detail is important, since it is carried by a scientist who made himself known for having called in the pages of the same scientific journal to seriously consider the hypothesis of a laboratory leak to explain the current pandemic. An origin that he now calls into question in view of his work which, according to him, provides “solid evidence in favor of an origin of the pandemic via a living animal”, present in this market.
The virus is believed to have spread mainly in the western sector of the market, partly occupied by vendors of raccoon dogs, a type of raccoon prized for its fur. The animal could be the desired intermediate host.
“In this city of 11 million people, half of the first cases are linked to a place the size of a soccer field,” said Michael Worobey. in the pages of New York Times. It becomes very difficult to explain this trend if the epidemic has not started in this market. “
A concordance of facts
“The lab leak may exist. It’s certain. This has already been seen, comments virologist Jean-Paul Gonzalez, a specialist in investigating the origins of pandemics and who teaches at Georgetown University. But there is, within the framework of this pandemic, a concordance of facts which, from the beginning, points to an origin of animal nature. “
The bat is the carrier of a high number of strains of coronavirus, strains that another animal, called host, would have allowed to pass into humans.
“For scientists, there are hypotheses that are easy to dismiss out of hand, such as the laboratory leak. But for politicians, it’s a bit more complicated, he adds. However, animal origin is no less serious. It is even a little more so, since it presupposes that there will be a SARS-CoV-3 in the future, then 4, then 5 … Hence the importance of finding good, and especially good understand the origin of this coronavirus ”without which the COVID-19 pandemic would not have existed.
In February 2020, two to three months after the first cases of contamination, Chinese researchers discovered in bats in Yunnan a strain of coronavirus called RaTG13 and 96.2% identical to SARS-CoV-2, the virus. at the origin of the current pandemic.
Last September, a new analysis published in the pages of the journal Nature confirmed the discovery made a year earlier by researchers at the Institut Pasteur who isolated three coronaviruses from bats in Laos that share great similarities with SARS-CoV-2. The genome of these three strains is 95% similar to that of SARS-CoV-2, and one of them, called Banal-52, is, with 96.8%, the closest relative of SARS-CoV- 2 never discovered to date.
“When SARS-CoV-2 was first sequenced, the receptor binding domain [région cruciale de la protéine de spicule qui permet au virus de s’accrocher à une cellule pour la contaminer] really looked like nothing we had seen before, explains in the article Edward Holmes, virologist at the University of Sydney in Australia. This has led some people to speculate on a virus created in a lab. But the Laos coronaviruses confirm that these parts of SARS-CoV-2 also exist in nature. “
The need for knowledge
For Christian Bréchot, president of the Global Virus Network, the COVID-19 virus “was probably in circulation since the end of August or the beginning of September 2019”, he said, from Tampa in Florida, where this virologist teaches at the University of South Florida. “But we can never know for sure because of the opacity and lack of access to samples held by China. “
Paradoxically, Beijing was quick to share the sequencing of SARS-CoV-2 with the rest of the planet, as of January 5, 2020, in order to allow its diagnosis everywhere on the planet. “But it was impossible to do research on the ground in China very early on. Consequence: two years later, we are still not able to find the host animal, which, under the circumstances, is not very usual. “
In the case of the first outbreak of SARS, between 2002 and 2004, the WHO managed to collect enough information 14 months after the start of the pandemic to establish a link between this coronavirus and the civet, the host animal that allowed the passage of this coronavirus between species.
Since the start of the current health crisis, the pangolin, mink, raccoon dog, civet, domestic cats or even ferret badgers have been singled out for their possible participation in the ongoing mass contamination.
“In the immediate future, knowing this animal will not change anything,” assures Mr. Bréchot. But from a global point of view, this remains important information since 70% of emerging infections are caused by transmission to humans from animals. It is therefore necessary to know as much as possible the animals which are involved in these transmissions ”, to be able to see them coming, to prevent them and to fight them.
Knowledge that could protect against future pandemics. In theory at least. “Over the past two years we’ve learned a lot, but are we going to learn the right lessons? asks Jean-Paul Gonzalez. In 1976, after the discovery of the Ebola virus, we understood everything about its virology, but that did not prevent from having 27 epidemics which killed more than 15,000 people, and this, mainly because of politics and the economy. But certainly not science, ”he concludes.