https://www.sciencetimes.com/articles/33905/20211012/china-r...
There's a lot of economic activity in China that is close to bat habitats and there's evidence that cross reactivity to sarbecoviruses exists in a significant amount in rural china.
The researchers collecting samples were a very tiny slice of the human-to-bat-virus exposure that is going on in China all the time.
And we know that SARS-CoV-2 doesn't last very long on surfaces, it isn't transmitted by fomites. It needs to be aerosolized and breathed in. It isn't likely that the researchers were collecting live viable virus in the samples that they brought back to the lab. What they were sequencing was overwhelmingly going to be "dead" mRNA.
The idea that the lab researchers were the initial Typhoid Mary of the pandemic is also simply not believable because it requires one to believe that they lived within a bubble EXCEPT for one trip to the wet market where the outbreak happened. They didn't start spreading it around their apartment building, they didn't infect people in restaurants, didn't infect elderly relatives who wound up in the hospital, etc.
It makes "more" sense that they deliberately genetically engineered the virus and released it in the wet market entirely on purpose.
Except that SARS-CoV-2's epidemiological dynamics are well-known to be overdispersed? Almost all lineages die out, and a few explode due to repeated super-spreader events. It's therefore unlikely that the first cluster will be discovered at the site of introduction. For example, SARS-CoV-2 was presumably first introduced to other continents at airports and seaports; but that's not where the first clusters were found.
There's also the question of ascertainment bias, whether cases were found in the wet market simply because that's where the authorities looked. I assume you've seen those endless debates, which seem basically unresolvable to me given the limited information available.
The infected lab worker causing exactly one massive superspreading event in the wet market without infecting anyone else, making it look exactly like zoonotic spillover, without leaving any other contacts around Wuhan is much less believable to me. That sounds like a thousand to one odds or much worse.
That's indeed unlikely, but it's a strawman. As I've noted repeatedly above, most lineages die out. If the introduction into humans occurred outside the market (naturally or otherwise), then it's quite likely that patient infected others outside the market; those lineages just died out. I remember Trevor Bedford showing genomic evidence of all the failed introductions into Seattle before the spread finally went exponential, early in the pandemic.
Pekar et al. is basically a more sophisticated version of your argument, with numerical models of the phylogenetic and epidemiological dynamics. I don't think it's convincing (since they chose their power law pretty arbitrarily), but at least they acknowledge and purport to model that stochasticity.
The theory was that it was a virus they'd have sampled from immunocompromised miners working in the same caves that the bats with the most closely related viruses inhabit. They had some references to a report with something like that happening some time prior.
It's so far the only theory I've read that seems to match the evidence.
The evidence doesn't seem to indicate that it was engineered, or that it was a product of gain of function research on animals. I think there would have been more solid evidence pointing in that direction by now, if that was the case. They would have published something related to it, or non-Chinese researchers connected to the lab would have known something.
Yet there's no evidence of any related animal resorvoir, and the virus was very well adapted to humans from the very start. And everything points to the virus passing through the lab somehow. Those things put together seems to point at them having sampled a virus that already made the jump to humans, and that somehow during the sampling, or retrieving the sample from storage, the virus escaped.