The conversationJun 18, 2021 11:03:05 am IST
A year and a half after the pandemic, we still don’t know exactly where the SARS-CoV-2 virus, which causes Covid-19, came from. The prevailing view so far has been that the virus “spread” from bats to humans. But there are increasing calls to investigate the possibility that it arose from a laboratory in Wuhan, China, where Covid first appeared in late 2019.
So what do we know for sure and what do we still need to find out?
But there are still many unanswered questions: we do not know how the virus got to Wuhan, how its sequence evolved to allow human infection, and under what conditions it infected the first people who crossed its path. And for each of these stages, we don’t know if there was a human contribution (direct or indirect).
Zoonotic transmission routes, in other words, the passage of viruses from animals to humans, are now widely documented worldwide. Scientists even consider it to be a main mechanism for diffusion of new viruses.
But the fact that the pandemic began in the vicinity of a major virus research center that specializes in studying coronaviruses with epidemic potential in humans, the Wuhan Institute of Virology, has led to another hypothesis, the theory of the lab leak. Laboratory accidents have already directed human infections, including 1977 H1N1 flu pandemic, which killed more than 700,000 people.
Which theory is correct? In the absence of definitive evidence, and without promoting conspiracy theories, there needs to be a serious international conversation about the origin of SARS-CoV-2.
The zoonosis theory
In the scientific community, the debate about the origin of SARS-CoV-2 began with the publication of two articles at the beginning of the outbreak.
The first, dated February 19, 2020, was published in the journal of medical sciences. The lancet. This article, signed by 27 scientists, highlighted the efforts of Chinese experts to identify the origin of the pandemic and share the results. The authors deplored “rumors and misinformation” about the origins of the virus and stated that they “strongly condemn conspiracy theories that suggest that Covid-19 does not have a natural origin.” The authors based their opinion on the first published sequence data, but did not detail the scientific arguments supporting a natural origin.
In March 2020, another article published in Nature medicine provided a series of scientific arguments in favor of a natural origin. The authors argued:
- The natural hypothesis is plausible, since it is the usual mechanism for the appearance of coronavirus.
- The SARS-CoV-2 sequence is too distantly related to other known coronaviruses to predict the manufacture of a new virus from available sequences.
- Its sequence shows no evidence of genetic manipulation in the laboratory.
This last argument can be questioned, since there are methods that allow scientists to modify viral sequences without a trace. These include cutting the genome into fragments which can then be joined together or, more recently, using the ISA protocol, whereby overlapping fragments are naturally attached in cells through homologous recombination: phenomenon in which two DNA molecules exchange fragments. Furthermore, genetic manipulation is not the only scenario compatible with a laboratory accident or a leak.
Meanwhile, the intense research that has been carried out for more than a year to try to test the zoonotic scenario has not been successful so far: all 80,000 animal samples, of about 30 species, they tested negative. The samples came from farm animals and wild animals from different provinces in China. But it is important to note that this large number of negative samples does not disprove the zoonotic scenario.
The laboratory theory
Early papers advocating the theory of laboratory accidents received little attention, perhaps because they came from groups like the Bulletin of the Atomic Scientists, what tends to be critical of technology, or outsiders like him DRASTIC team (an acronym for “Decentralized Radical Autonomous Search Team Investigating Covid-19”).
Compound 24 Self-styled “Twitter Detectives” which are mostly anonymous with the exception of some scientists who participate under their real names, the DRASTIC group was formed on Twitter in 2020 and has set itself the mission to explore the origins of SARS-CoV-2. The information and arguments of the group have been examined in their own right, taken up and developed by some virologists, microbiologists other science communicators.
The first scientific articles discussing the possibility of a laboratory accident appeared in peer-reviewed scientific journals in July and August 2020: one of them is co-author of the author of this article, Etienne Decroly. The laboratory leak theory won out against traction after a May 13 magazine article Sciences, signed by 18 scientists, again called for the origins of SARS-CoV-2 to be examined.
So is it possible? Several elements related to the appearance of the virus raise questions. In particular, it has been established that the Wuhan Institute of Virology was driving virus close to SARS-CoV-2 collected in southern China.
In addition to direct genetic manipulation, a laboratory accident could also have occurred as a result of infection during collection in the wild or during an experiment with a virus that evolved in cells or mice in the laboratory, without necessarily directly manipulating its genome.
How can we know for sure?
In an investigation earlier this year, a joint commission between China and the World Health Organization (WHO) failed to identify the cause of the pandemic. concluding that a zoonotic origin is more likely and that the hypothesis of a laboratory accident is highly unlikely. But WHO Director-General Tedros Adhanom Ghebreyesus announced that he had you still ask that “will need to be addressed through additional studies.”
Determining whether SARS-CoV-2 has escaped from a laboratory will require a more in-depth investigation in which researchers have access to sequence databases, as well as the various resources used by Chinese researchers, including lab notebooks. , projects presented, scientific manuscripts, viral sequences. , order lists and biological analysis. Unfortunately, the sequence databases for SARS-CoV-2 have been inaccessible to scientists since September 2019.
In the absence of direct evidence, alternative approaches can provide additional information. By analyzing in detail the available sequences of coronaviruses similar to SARS-CoV-2, it is possible that the scientific community will reach a consensus based on solid clues, as they did for other outbreaks. including the 1977 H1N1 virus.
Biological black boxes
Whether the origin is zoonotic or not, it is necessary to question the consequences of our interactions with ecosystems, the industrialization of intensive farming, the safety protocols in the collection and experimentation of potentially pandemic viruses, and the proliferation of high-security laboratories. . particularly those near megacities.
We need to equip facilities that study viruses with security systems as demanding as those used to study nuclear energy. This could include the introduction of “Biological black boxes”, similar to flight recorders that allow investigators to recreate the final moments of a plane crash. Access to certain high-risk laboratories may depend on detailed digital descriptions of the experiments; sequencing data could be systematically archived; Laboratory air filters could be collected and, if there is a suspicion of pathogen spread, the genetic material on their surface could be sequenced.
These new security measures must be implemented internationally to limit the risk of future pandemics. As for SARS-CoV-2, it is important to trace its exact origins to precisely understand what defects may have led to its spread.