[WION] To date, no one has stated the urgent universal need to aggressively investigate the true origin of SARS-CoV-2, the coronavirus responsible for COVID-19, better than Karl and Dan Sirotkin in their August 12, 2020 article "Might SARS‐CoV‐2 Have Arisen via Serial Passage through an Animal Host or Cell Culture?""Despite claims from prominent scientists that SARS‐CoV‐2 indubitably emerged naturally, the etiology of this novel coronavirus remains a pressing and open question: Without knowing the true nature of a disease, it is impossible for clinicians to appropriately shape their care, for policy‐makers to correctly gauge the nature and extent of the threat, and for the public to appropriately modify their behaviour."
As the authors correctly note, serial passage, that is, the repeated re-infection within an animal or human population allows a virus to specifically adapt to the infected species.
That process occurs naturally in the wild, but it can be greatly accelerated in the laboratory by deliberate serial passaging of viruses in cell culture systems or animals, potentially leaving few or no traces as to whether the adapted viruses are naturally-occurring or laboratory-manipulated.
That type of "gain of function" experimentation can become particularly dangerous if viruses are adapted for human infection by serial passaging them through cell cultures and animal models that have been genetically-modified to express human receptors.
There are numerous scientific publications describing serial passaging of coronaviruses through "humanised" cell cultures and animal models, thus potentially creating a new coronavirus "pre-adapted" for human infection.
At present, the scientific consensus is that SARS-CoV-2 came from bats, but how it evolved to infect humans remains unknown.