When a novel coronavirus was first identified in late 2019, the assumption was that, like most epidemics, it was of a zoonotic source. A few studies, including one published in the prestigious Nature magazine, concluded that the virus is not a laboratory construct.
Today, claiming a non-zoonotic origin is widely considered a conspiracy theory, and indeed many such claims are easily refutable without requiring probabilistic inference.
... More LessThere have been many more viruses introduced to humanity zoonotically than through lab failures. Specifically, there were several major pandemics involving novel coronaviruses from natural origin in recent years. Although there have been no known outbreaks involving any novel viruses (coronavirus or otherwise) that came from a lab, there have been cases of lab leaks that were caught before causing widespread infections, including one lab leak (of a previously known virus) that led to secondary infections. There are also no known cases of a virus being released deliberately in modern history.
Before examining the specific evidence, the initial estimate of the probabilities of Zoonotic : Bioweapon : Lab (based on their respective likelihood of incidents per year) is 200:40:3, or 82%:16.5%:1%.
COVID-19 is more contagious than the typical flu, but not as fatal as recent viruses like MERS or SARS. Overall, it is not particularly well-suited as a traditional bioweapon, and COVID-19 broke out during a relatively peaceful time. This indicates that, if it was used as a bioweapon, it would probably not be released as a method of killing people but for a different purpose such as disrupting the world economy.
The COVID-19 outbreak was first recorded in Wuhan, one of the larger cities in China. Large cities are often the initial breakout sites of zoonotic pandemics, but in that sense Wuhan is no more likely than any other city. It also isn't a particularly desirable target for releasing a bioweapon.
However, Wuhan stands out for housing the Wuhan Institute of Virology, one of only a few labs engaged in gain-of-function research.
There are no obvious natural sources for COVID-19 in the Wuhan area (Hubei province). The most similar coronavirus is found among bats that don’t live nearby, and scientists have not been able to pinpoint the exact point where SARS-CoV-2 transferred to humans. On the other hand, the initial cluster of cases in the Wuhan wet market is significantly more likely if the virus originated zoonotically.
SARS-CoV-2 has parts in common with two different viruses, but those individual viruses do not share these similarities with each other, indicating it is a chimera. Such chimeras are found both in nature and in labs that conduct gain-of-function research. However, this specific chimera seems less likely to combine in nature, as it requires interaction between hosts that do not usually cohabitate.
SARS-CoV-2 has a furin cleavage site - an amino acid sequence that causes the protease furin to cut the virus in a way that facilitates its entry into cells. This feature is missing in related coronaviruses, and its placement in the genetic code looks like an insertion rather than a mutation, making it less likely to develop in nature.
There is some weak evidence regarding lax security and procedures at the Wuhan Institute of Virology.
The WIV explicitly stated that they were not working on SARS-CoV-2 prior to the outbreak.
However, on December 30, when Dr. Shi Zheng-Li was informed of the COVID-19 outbreak, changes were made to her bat virus database, making it look like she was trying to dissociate her lab's research from the COVID-19 outbreak.
Then, in January 2020, WIV researchers published a paper claiming to have found a previously unknown coronavirus named RaTG13 that was a 96% match with SARS-CoV-2.
But RaTG13 is a new name given to BtCoV/4991, a coronavirus that the WIV discovered (along with many other viruses) when they examined a bat cave after six miners contracted a pneumonia-like disease and three died.
This, and other anomalies surrounding WIV’s handling of RaTG13, are indicative of attempts to minimize WIV involvement.
The official Chinese response was not transparent, though not particularly surprising even if the virus developed zoonotically. They restricted WHO access, destroyed samples, and withheld information, which might be construed as an attempt to hide evidence that could be used to blame China for COVID-19. Additionally, they sent Major General Chen Wei from the Academy of Military Medical Sciences to oversee COVID-19 efforts at the WIV, which could potentially indicate the involvement of a bioweapon, but it is probably immaterial.
No one from the Wuhan Institute of Virology was reported as being infected with, or dying from, COVID-19, reducing the likelihood that there was a lab escape.
No one has come forward to give first hand testimony or evidence of any link between COVID-19 and a lab, even though some doctors and researchers have spoken out about other incidents where they believed that China mishandled information regarding COVID-19.
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