Consider, too, the unique furin cleavage site between the S1 and S2 subunits of the SARS-CoV-2 spike protein. Furin is an enzyme expressed by human cells that separates the spike protein subunits at the cleavage site, enabling the virus to bind more efficiently to human cells and release its genetic material into them. It is an important reason that SARS-CoV-2 is so easily transmissible.

The furin cleavage site is found nowhere else in the entire genus of SARS-related betacoronaviruses. SARS-CoV-2 is the only one that has it. This fact alone suggests that it did not arise naturally in SARS-CoV-2. In addition, while other, more distant coronaviruses do have furin cleavage sites, the protein components (amino acids) in the SARS-CoV-2 furin cleavage site are coded for by a unique set of nucleotides in its RNA, not found in the other viruses, making natural recombination between the viruses unlikely.

It’s particularly concerning that in 2018 the EcoHealth Alliance reportedly submitted a proposal to the Defense Advanced Research Projects Agency (DARPA) to partner with the WIV in constructing SARS-related bat coronaviruses by inserting such cleavage sites into their spike proteins. DARPA rejected the proposal because it failed to address the risks of gain-of-function research. EcoHealth’s president, Peter Daszak, did not dispute details of the reporting.