After six months of exhaustive investigation, the global scientific community has been unable to identify the natural source of COVID-19, that is, the when, where and how it "jumped" from animals to humans.
Some now imply that we may never know the natural origin of COVID-19.
In a news article recently published by the international science journal Nature, the progress, or lack thereof, identifying the natural source of COVID-19 was reviewed.
According to the article, COVID-19 probably originated in bats, specifically horseshoe bats, which host two closely related coronaviruses, named RaTG13 and RmYN02, whose genomes are 96% and 93% identical to COVID-19, respectively.
Both coronavirus samples were isolated from bats in Yunnan Province, RaTG13 in 2013 and RmYN02 in 2019, and were studied in the Wuhan Institute of Virology.
Wuhan is where the outbreak of COVID-19 originated and about 1,000 miles from Yunnan.
The Nature article does not mention that RaTG13 is actually a duplicate of another bat coronavirus, BtCoV/4991, about which there is nearly no published experimental data since it was isolated in 2013, despite clearly being a Potential Pandemic Pathogen.
That is, except for the structure, analyzed only by Chinese scientists, practically nothing is known about RaTG13.
The Nature article also does not mention that the receptor-binding domain of RmYN02 showed only a 61.3% sequence identity with COVID-19, meaning it is highly unlikely that RmYN02 could even bind to human cells.
The Nature article suggests that pangolins (scaly anteaters), might be an intermediate host because some pangolin coronaviruses “share up to 92% of their genomes” with COVID-19, presumably bridging the gap between bats and humans.
When asked about that possibility, Dr Ralph Baric, a coronavirus expert from the University of North Carolina, in a March 15, 2020 interview, stated unequivocally that pangolins were not the source of COVID-19:
“Pangolins have over 3,000 nucleotide changes - no way they are the reservoir species [for COVID-19], absolutely no chance.”
Nevertheless, the receptor-binding domain of COVID-19 is structurally closer to pangolins than bats indicating a recombinant event, in this case, likely artificial.
In fact, Ralph Baric and Zheng-Li Shi, the “bat woman” from the Wuhan Institute of Virology, conducted just such an artificial receptor-binding domain insertion from a newly isolated bat coronavirus (SHC014) onto the “backbone” from SARS-CoV, the coronavirus responsible for the 2003 pandemic.
In a December 9, 2019 interview, Dr Peter Daszak, President of the EcoHealth Alliance and a long-time collaborator with the Wuhan Institute of Virology, presumably referring to the Ralph Baric- Zheng-Li Shi experiments, stated “you can manipulate them in the lab pretty easily” inserting a spike protein “into a backbone of another virus.”
Thus, an artificial recombinant event carried out in the laboratory would be a far better explanation of pangolin-like structures appearing on a bat coronavirus backbone than one occurring in nature, at least given the current state of knowledge.
The most conspicuous sign of COVID-19 genetic manipulation is the presence of a furin polybasic cleavage site, a structure that is not present in any of the coronaviruses so far identified as possible direct ancestors.
The authors of the RmYN02 article stretch credulity even further by claiming that RmYN02 has a precursor cleavage site.
In reality, it is a weak attempt to offer a naturally-occurring explanation for the presence of the furin polybasic cleavage site in COVID-19.
Unfortunately, the amino acid sequence PAA, the insertion cited by the authors, is chemically neutral, totally unlike COVID-19's polybasic PRRAR sequence and PAA has no ability to cleave anything.
Based on the actual evidence, it is unlikely that RmYN02 is a natural close relative of COVID-19.
Although COVID-19 appears to have been “pre-adapted” for human infection, the artificial insertion of the furin polybasic cleavage site may explain a potentially significant point mutation in COVID-19 that may have increased its infectivity.
According to the article “The D614G mutation in the SARS-CoV-2 spike protein reduces S1 shedding and increases infectivity,”, over the course of the human pandemic, one amino acid position has changed from aspartic acid to glycine, increasing the stability of the spike protein and, thereby, making COVID-19 more infectious.
As suggested by the authors, that mutation may have been what is known as a “positive selection” to compensate for the structural instability created after the artificial insertion of the furin polybasic cleavage site.
The burden of proof is now on China to demonstrate that COVID-19 is naturally-occurring because most of the available evidence indicates otherwise.