There are many more coronavirus hosts in the animal world than previously thought.
In any case, this is the conclusion reached by an artificial intelligence (AI) which has been tasked by a team of scientists from the University of Liverpool to hunt down mammals likely to give birth to the future Sars, Sars-CoV -2 or Mers-CoV.
Race result: "There are 40 times more species likely to have at least four forms of coronavirus in them than was already established, and about 30 times more mammals in which Sars recombination could occur- CoV-2 [to give birth to a new virus, Editor's note] ", write these researchers in an article published Tuesday, February 16 by the journal Nature Communication.
All mammals under the magnifying glass of AI
They developed this algorithm to fill in the gaps "in our limited knowledge of which mammals are potential hosts for which coronaviruses, which is necessary to understand where recombinations of these viruses can occur to form new ones," explains Marcus Blagrove, virologist at the University of Liverpool and one of the co-authors of the article, contacted by France 24. The proof: "Before the arrival of Sars-CoV-2, we had very little interest in the pangolin ", adds Maya Wardeh, lead author of the study, also contacted by France 24.
There are simply too many mammals on Earth for humans to study them all.
Not to mention that "some are in countries which do not have the necessary budgets to do this kind of research", specifies Maya Wardeh.
An obstacle which is not likely to frighten an algorithm fed on "big data".
The two researchers provided their in-house AI with a considerable amount of data on all of the mammals listed - biological proximity to other animals known to be carriers of coronavirus, geographic area where they live, or even life expectancy - and made same with known viruses.
The machine then provided the most complete map to date of all rodents, carnivores, bats, or even artiodactyls (cattle, hippos) which may be reservoirs for several coronaviruses.
More precisely, "the model calculates the probability for each species of mammal to be infected with each of these viruses, which allows us, then, to predict which ones can be hosts for several coronaviruses at the same time", explains Maya Wardeh .
On average, each coronavirus can have 12.5 carrier mammals and each animal studied can be infected with 5.5 different viruses, according to these calculations.
An efficient algorithm
For Sars-CoV-2, the AI estimated that there are 126 potential hosts in the wild, or ... 122 more than what was accepted when the Liverpool researchers got down to work in the summer. 2020. The little Asian yellow bat, the hedgehog or the European rabbit should, for example, be added to the list of potential carriers of Sars-CoV-2.
This work also made it possible to identify the most important coronavirus "pots" in the animal kingdom.
Bats, of course, are right at the top of the list.
Some of them can be infected with 68 different coronaviruses.
This is the case of the greater horseshoe, or great horseshoe, the largest species of bat present in Europe.
More surprisingly, the domestic cat has also been identified as being particularly permeable to these viruses by the algorithm of British researchers.
It is a potential host for 65 coronaviruses, including Sars-CoV-2.
This feline is, for the authors of the article, one of the main "underestimated risks" to become the cradle of a new virus, the result of a mixture of those which would be present in its body.
Admittedly, these results are the result of calculations by a machine and not observations in the field.
"Obviously these conclusions are not 100% correct," admits Maya Wardeh.
But the two researchers are confident in the robustness of their model.
Since they developed it, the scientific community has discovered several new hosts of Sars-CoV-2, such as mink, and "in most cases, they had been identified by the algorithm," Marcus points out. Blagrove.
No feline threat
“That doesn't mean you have to stop stroking your cat!”, Insists Maya Wardeh.
It is not because the tomcat is potentially very permeable to a large number of coronaviruses that it will necessarily catch them.
In particular, it would have to be in the vicinity of another mammal that transmits the virus to it, and for a pet, which often leads a home life, such occasions are rare.
In addition, this model does not predict the likelihood of new coronaviruses appearing in these legged reservoirs.
"All we do is indicate in which animals this can occur. Calculating the actual risk is infinitely more complex", specifies Marcus Blagrove.
Nor is it clear from their work whether the result of a possible recombination will be a more virulent Sars-CoV-2 or one of the many coronaviruses that, at worst, cause a cold in humans.
"We need a bioinformatician capable of anticipating the characteristics of the result of this possible mixture", explains the virologist.
The algorithm's predictions may give the impression of an animal kingdom even more dangerous than it was to our health.
But this is not the aim of the efforts of British researchers.
"We are only describing a phenomenon that already exists in nature - the recombination of coronaviruses - and specifying which, in our opinion, the species which should be the subject of special surveillance", summarizes Marcus Blagrove.
And so not to be, as with Sars-CoV-2, caught off guard that the coronavirus had come.
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