For the thousandth time, no: the coronavirus SARS-CoV-2 was not created in a laboratory. Finally we got researchers’ confirmation. Andersen and colleagues published on Nature Medicine the evidence that SARS-CoV-2 is just the seventh coronavirus able to infect humans. Together with SARS-CoV and MERS-CoV, the novel SARS-CoV-2 causes more severe symptoms, while HKU1, NL63, OC43 and 229E are associated with mild symptoms. In the article, researchers investigated the genome of SARS-CoV-2, in comparison to the other coronaviruses. They focused on the Spike protein, which allows the virus to bind to the ACE2 receptor on the cell surface (the first step of infection). Both SARS-CoV and SARS-CoV-2 exploit ACE2 for cell anchoring, but the binding to the receptor occurs in a completely different way for the novel coronavirus. If it was genetically manipulated, it is conceivable that a pre-existing strategy would have been employed (it would have been extremely difficult and time-consuming to create a new one from scratch). Instead, SARS-CoV-2 presents a novel backbone, different from other existing ones. Authors conclude that the origin of the virus is due to one of the two following options:
- natural selection in an animal host before zoonotic transfer (to humans). First Covid-19 cases were linked to the Huanan market in Wuhan. Regarding this, there are a couple of plausible options. First, human and bat SARS-CoV-2 are almost genetically identical, even though the way of binding to ACE2 is different. Second, pangolin SARS-CoV-2 binds to ACE2 in the exact same way as the human virus, but neither bat nor the pangolin viruses have a feature in the Spike protein that instead is present in the human version (this feature is related to the activation of the Spike protein by TMPRSS2).
- natural selection in humans following zoonotic transfer (from animal). Another possibility is that a precursor of SARS-CoV-2 “jumped” into humans and then strengthened and adapted itself to the novel host organism. This possibility implies a first infection earlier than the first Covid-19 cases diagnosed in November/December 2019. To this purpose, retrospective serological studies could provide some answers.
At the moment, the most plausible option is that the human SARS-CoV-2 originated from the pangolin virus (because of the identical anchoring mechanism) and then evolved through mutation and recombination events that created the novel human-specific features.