FWIW, Gideon Meyerowitz-Katz has a Substack post in which he goes through his opinion of what likely caused the outbreak of Covid-19.
He caveats everything he says by downplaying his own credentials (unlike many of the lab-leak proponents who, if they have any credentials at all, stretch them beyond breaking point), before looking at three possible scenarios and giving his own off-the-cuff probabilities for the likelihood:
Theory 1: China Created COVID-19
My Rating For Possibility: <1/100
He gives this the lowest possibility and specifically talks about the claims made by the Trump administration:
His responses to each one:
1. "The first of these claims is straightforwardly false. The claim is that the furin cleavage site of the COVID-19 virus - an element of SARS-CoV-2 that is
critical to its success in infecting people - is not found in nature, and therefore the virus cannot have evolved naturally.
It is true that furin cleavage sites are rare in the family of viruses that SARS-CoV-2 comes from. In particular,
in bat coronaviruses that mostly do not infect human cells that are related to SARS-CoV-2 directly, there are no other examples with this specific feature around.
But there are many other coronaviruses that have evolved furin cleavage sites. For example, two of the human coronaviruses that circulate every year causing colds have precisely this feature.
Here’s a paper from 2015 describing the potential problems that the furin cleavage site of HCoV-OC43 could have for human neurological cells.
While it’s true that this feature is somewhat unusual, that’s entirely expected. If furin cleavage sites evolved all of the time, we’d be inundated with pandemics. Instead, most bat viruses just infect bats, and never evolve features that could cause them to be dangerous for humans."
2. "The second point from the White House propaganda site is also untrue. The
best current evidence indicates that there were almost certainly two or even more introductions into humans at the onset of the pandemic. While this sort of genetic epidemiology is complex, the data shows that there were two distinct lineages of SARS-CoV-2 spreading in November and December 2019, which could only happen if there was more than one introduction into the population at that time."
3. "Point three is entirely speculative. We’ll cover the “biosafety” concerns more in the next section, but even without looking too deeply into the evidence you can’t infer much from this sort of statement."
4. "Point four is astonishingly misleading. COVID-like symptoms encompass almost the entire spectrum of human illness, and therefore it is entirely meaningless to say that there were a few people sick in Wuhan in August-October 2019. It’s a large lab, of course people were sick. The average human adult is estimated to have
3-4 symptomatic colds per year, most of which happen in the colder months. Moreover, there is
no evidence whatsoever of a COVID-19 outbreak in the WIV in 2019. "
5. "The final point is simply a matter of opinion. Most of the experienced virologists I know believe that SARS-CoV-2 came from a zoonotic outbreak. The White House prefers to trust the small minority of experts who think differently. That’s not evidence, and so we cannot really appraise it as such. We’ve now had five years for proponents of the lab leak conspiracy to find literally any evidence that the virus was designed. It should be trivially easy to prove. "
Theory 2: A Big Accident
My Rating For Possibility: 5/100
Theory 3: Zoonosis
My Rating For Possibility: 95/100
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