In an open letter published on Science On May 14, 2021, 18 scientists from all over the world called for greater transparency on the origins of the SARS-CoV-2 coronavirus, and called for a broader, independent and in-depth investigation that takes into account all hypotheses on the ground, including that of one spillover (a “leak”) of the virus from a biosecurity laboratory.
The idea behind this appeal, as well as a previous request published in March on the New York Times, is that the theory of the “virus escaped from the laboratory” should be analyzed with care, even if only to disprove it completely, because it is part of the scientific method to interrogate even the apparently more solid hypotheses and consider, before discarding them, even the least probable ones. But we are moving on politically impervious terrain, and after Biden’s request for a new investigation into the origin of the covid to American intelligence, conspiracies have resurfaced that we believed archived on an elusive artificial virus.
An unsuccessful mission. For the avoidance of doubt, the consensus of the scientific community on the animal origin of the SARS-CoV-2 coronavirus is almost unanimous. However, it is worthwhile to understand what are the reasons that have made the laboratory hypothesis revive. Much of the discontent of those who raise these doubts stems from the WHO’s difficult mission in Wuhan last January, which left scientists anxious for answers unsatisfied. It is common opinion that the organization’s experts had little time available and were subjected to political pressure, which resulted in the hasty dismissal of some leads and the recovery of hypotheses deemed unlikely (we wrote about it here).
Some suspicion, no evidence. The proximity of the Wuhan Institute of Virology to the Huanan fish market, the first major outbreak of CoViD-19, is one of the main motivations of the proponents of the laboratory theory. The institute is one of the most active in the world in research on bat coronaviruses (including RaTG13, the closest known relative of SARS-CoV-2, although not a direct progenitor), but it has some scientific publications on pathogens behind it. respirators of animal origin in Yunnan are not always consistent with each other.
However, from here to hypothesizing the existence of “secret” experiments that ended badly there is an abyss: there is no scientific proof that the Wuhan laboratory was working with viruses closely related to SARS-CoV-2. RaTG13 has a genetic similarity to the new coronavirus of 96.2%, too little to be a direct relative, and moreover, WHO experts were able to access the Wuhan Institute of Virology and confirm the integrity of the safety protocols.
Made to measure? Proponents of the laboratory theory also point out some molecular peculiarities of the novel coronavirus, such as the fact that it is the only specimen, among the Sarbecovirus (a subgenus of coronaviruses) to feature a furin cleavage site, which is a part of the spike protein that helps it make its way into the host’s cells. Or that another region of the spike defined receptor binding motif (RBM) seems particularly suited to docking with human cells, an ease of docking that the SARS coronavirus, SARS-CoV-1, conquered only long after making the leap into humans.
The simplest explanations. These characteristics make SARS-CoV-2 appear pre-adapted to infect humans, as if – some go so far as to say – it had already been able to to train on human cells in the laboratory. In reality, the molecular characteristics mentioned are perfectly explainable with i typical mechanisms of evolution and recurrent in viruses found in nature. As confirmed by the New Scientist David Robertson, evolutionary virologist at the University of Glasgow, furin cleavage sites are widespread throughout the coronavirus family (a virtually identical fragment was recently found in a bat Sarbecovirus in Thailand) and have evolved many times independently in different lineages. They have been favored on multiple occasions, of course, by evolution.
The presumed unnaturality of some characteristics of the virus may depend on the recombination of genetic material, a phenomenon known for RNA viruses: when two viruses attack the same cell, they can exchange substantial parts of the genetic code and give rise to unpublished sequences. Including this mechanism, “it is very clear to anyone who has worked in this field, that SARS-CoV-2 is just another sibling lineage of the first SARS virus to emerge in 2002,” says Robertson. And it’s not that the virus is pre-adapted to humans, it’s simply a generalist guy, which knows how to live in humans as well as in minks, cats, pangolins and probably other mammals.
The Moon and the finger. The most likely hypothesis is that a direct ancestor of the new coronavirus is present in nature and has yet to be discovered: but given the amount of coronaviruses dangerous to humans, it’s like looking for a needle in a haystack and it could take decades to find it. The momentary absence of evident evidence on host animals is perhaps the reason that most of all fuels conspiracies: as repeatedly observed during the pandemic, we are not used to being in uncertainty and we are satisfied, rather, with easy shortcuts. Certainly the laboratory hypothesis is, in a completely theoretical way, possible, but focusing on it, with hundreds of viruses in nature probabilistically ready to make a species jump, could be a false solution.