New genetic clues link the origin of Covid-19 to bats

Magazine Nature has just published a French paper that supports the hypothesis that the SARS-CoV-2 coronavirus, which causes the Covid-19 infection and a pandemic that has so far caused the death of around 5.8 million people throughout the world. planet, It will have an origin in bats (or bats) that live in the limestone caves of Southeast Asia and southern China..

Researchers from the Pasteur Institute in Paris describe in that work (Bat coronaviruses related to SARS-CoV-2 and infectious for human cells) coronaviruses genetically similar to SARS-CoV-2 and identified within bat populations in northern Laos. The study suggests that these new bat coronaviruses may have a potential to infect humans similar to that of the first strains of SARS-CoV-2.

Marc Eloit and his colleagues at the Pasteur Institute have analyzed a sample of 645 bats (belonging to 6 families and 46 species) that live in caves in northern Laos and have found in them, specifically, three viruses that they consider closely related to SARS-CoV-2. The authors describe that the genetic sequences encoding the ACE2 binding regions in the new viruses are similar to those of SARS-CoV-2; ACE2 is a human cell receptor that SARS-CoV-2 uses to enter cells. Bat viruses can bind to human ACE2 receptors more efficiently than the original SARS-CoV-2 strain isolated from humans. They have also observed that one of these viruses replicates within human cell lines but is inhibited by antibodies that neutralize SARS-CoV-2.

The “most likely scenario” for the WHO

It should be remembered that on March 31, 2021, the WHO published its final report on the mission in China to discover the origins of SARS-CoV-2, in which it concluded that The most likely scenario is that transmission of the virus from bats to humans occurred through one or more unidentified intermediate animals.. He also described the theory that it escaped from a laboratory as “extremely unlikely”, assuring that the virus was not circulating in Wuhan, China (the epicenter city of the pandemic and where the headquarters of the Wuhan Institute of Virology is, which investigates with various types of coronavirus), before December 2019.

However, the director general of the WHO, Tedros Adhanom Ghebreyesus, declared then that, as far as this organization is concerned, “all hypotheses are still on the table. This report is a very important beginning, but it is not the end. We have not yet found the origin of the virus, and we must continue to follow the science and leave no stone unturned as we do so.”

In fact, the WHO report presents four possible theories about the appearance of the SARS-CoV-2 coronavirus in humans, without ruling out any of them completely: it is “possible or probable” that the origin was a direct contagion from an animal to a human; it is “likely or very likely” that there was an intermediary animal between an infected animal and humans; it is “possible” that the virus has reached humans through food products, and it is “extremely unlikely” that the virus has reached humans due to an incident in a laboratory.

Jordi Serra Cobo, professor at the Department of Evolutionary Biology, Ecology and Environmental Sciences and at the Biodiversity Research Institute of the University of Barcelona (UB) and a reference in coronavirus, in statements to this newspaper at the beginning of the pandemic (in April 2020) said: “The certainty we have is that the virus has an animal origin. The epidemic manifested itself in Wuhan but at the moment we do not have enough information about the initial infection to determine its origin with certainty.” And added: “The origin of the ancestor that has given rise to SARS-CoV-2 is a bat. Now, we do not know what the intermediate species is; it may have been the food consumption of the intermediate species. The SARS-CoV epidemic was caused by the consumption of the civet, a mammal the size of a wild cat. It is a gastronomically highly appreciated animal, which is displayed alive in restaurants so that diners can choose the specimen they want to eat”.

Today, after reading the new article of Natureexplained that “I know the team from the Pasteur Institute that has participated in this research, I have even worked with some of them on European projects. It is a very good team. Southeast Asia is one of the hottest regions epidemiologically speaking, where a great diversity of viruses is concentrated, including coronaviruses. In an article published by Souilmi et al. in 2021 in the magazine Current Biology, the authors found in the human population of Southeast Asia genes that interact with coronaviruses for about 20,000 years. This agrees with the findings of Marc Eloit’s team and with the denomination of hot spot of this region. Coronaviruses have been circulating in wildlife and human populations in Southeast Asia for centuries.“.

Direct transmission from bat to human?

Serra-Cobo also reports that betacoronaviruses are a genus of coronavirus that includes SARS and that, it seems, their origin is in bats. However, he assures, “the direct transmission of a coronavirus from a bat to a human has never been observed.”

“In that sense, the that bats capable of infecting our cells have been found does not mean that there has necessarily been a jump from bat species to human. Taking into account that the human-bat interaction is relatively small, there may be an intermediate species that is closer to human activity and that is the transmitter. In any case, it should be borne in mind that biological compatibility to infect our cells is not a sufficient factor for an epidemic to occur. It is important that there be an amplification and further spread of the pathogen, anthropic-type factors that are closely related to our activity”, he concludes.