As folks go back and forth on the origin of the current viral pandemic there is a recent paper that some use to justify a natural origin. In this paper they state:
The emergence of SARS-CoV-2 differs markedly from documented laboratory escapes that, with the exception of Marburg virus24, have been of readily identifiable viruses capable of human infection and associated with sustained work in high titer cultures25–27. No previous epidemic has been caused by the escape of a novel virus and there is no data to suggest that the WIV—or any other laboratory—were working on SARS-CoV-2, or any virus close enough to be the progenitor, prior to the COVID-19 pandemic. Viral genomic sequencing without cell culture, which was routinely performed at the WIV, represents a negligible risk as viruses are inactivated during RNA extraction28 and no case of laboratory escape has been documented following the sequencing of viral samples. Known laboratory outbreaks have been traced to both workplace and family contacts of index cases and to the laboratory of origin25–27,24. Despite extensive contact tracing of early cases during the COVID-19 pandemic, there have been no reported cases related to any laboratory staff at the WIV and all staff in the laboratory of Dr. Shi Zhengli were reported to be seronegative for SARS-CoV-2 when tested in March 202010. During a period of high influenza transmission and other respiratory virus circulation29 reports of illnesses would need to be confirmed as caused by SARS-CoV-2 to be relevant. Epidemiological modeling suggests that the number of hypothetical cases needed to result in multiple hospitalized COVID-19 patients prior to December 2019 is incompatible with observed clinical, genomic, and epidemiological data20. The WIV possesses an extensive catalogue of samples derived from bats and has reportedly successfully cultured three SARSr-CoVs from bats, all of which are genetically distinct from SARS-CoV-230–32. These viruses were isolated from fecal samples through serial amplification in VeroE6 cells, process that consistently results in the loss of the SARS-CoV-2 furin cleavage site33–39. It is herefore highly unlikely that these techniques would result in the isolation of a SARS-CoV-2 progenitor with an intact furin cleavage site. No published work indicates that other methods, including the generation of novel reverse genetics systems, were used at the WIV to propagate infectious SARSr-CoVs based on sequence data from bats. Gain-of-function research would be expected to utilize an established SARSr-CoV genomic backbone, or at a minimum a virus previously identified via sequencing.
First and most important, all earlier viral work, say a decade ago, did not have the ability to do what can be done today with bio-technology. We can now splice, insert, and so forth, and China has shown great leadership in this field. Thus the argument that it never happened before is specious at the very best and in my opinion useless.
Second the furin issue is a a key one which in my opinion the authors dismiss out of hand.
Third, and this is key, the last sentence asserts a "fact not in evidence". It assumes something that justifies their conclusion.
I am far from having an answer, the data is lacking and one would now guess unattainable. But just from a simple reading of the text one sees major faults in the basic logic and defects in the evidence as well as an attempt to ignore the the clinical expertise of the Chinese in this area.
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