>>>1) A disease traveled hundreds of miles to a large city without leaving a trace of evidence

This doesn't strike me as intrinsically unlikely. Bats can apparently fly ~50 miles for food, a person on a bus can easily travel ~400 miles in a day, etc. I don't disagree with the premise that a lab outbreak is possible, but so is "guy got infected by bats or something, didn't realize, hopped on a bus to visit family/find work".

And that bus happened to be traveling to a city which hosts a top-tier biolab with the world's foremost experts on bat-borne coronaviruses. Not a smoking gun, of course, but anyways I think your logical fallacy here is the "reasonableness" heuristic, in which you base the likelihood of some incredibly unlikely event on whether you can "imagine" some scenario where it happened. The fact that you can come up with a story to explain... well, I don't even know exactly what you're explaining, because it's really just a fragment of a chain of causation which has been mostly left unsaid. But anyways, I'm willing to wager that you know very little about disease transmission patterns so your intuition here is worse than ignorance.

The OP specifically said "in the absence of evidence we need to ask ourselves which is more likely..." - and suggested (strongly) that a lab outbreak is much more likely than the alternatives. I was trying to point out that a) once the virus is in humans it's easily spread and b) though the lab's research may have led to the pandemic, it doesn't necessarily follow that there was a "lab outbreak".

Here's my understanding on what (probably?) happened:

1) Bat(s) carrying the novel coronavirus were taken from Yunnan or Zhejiang province.

2) They were brought to the lab in Wuhan (WHCDC) (~500+ miles away).

3) They were experimented upon, dissected for tissue samples, etc.

4) Some/all of these samples were disposed of.

And some time later, the Huanan Seafood Market (near this lab) was likely an origin point of the epidemic.

Now, the actual disease release could happen at any of the 4 steps above. Someone who captured the bats could have been infected at that time. Someone could have been exposed during transport of the bats. Someone could have been infected during experimentation. The materials could have been improperly disposed of, tainting food/water/clothes/whatever. Would we consider all of those "lab outbreaks"?

Also, I want to point out - "a city which hosts a top-tier biolab with the world's foremost experts on bat-borne coronaviruses" - we may also expect such a biolab to be located in an area where bats, and bat-borne viruses, are more likely to be, no? Where else would be a more logical place to put it? :)

But is it more likely for the virus to have undergone sufficient natural mutation from its closest known relative* (RaTG13) in order for it to have become both capable of and very effective at infecting humans (ACE2 receptors) and for it to have then been so carelessly disposed of from the BSL-4 Wuhan biolab that someone came into contact with it and became infected, or is it more likely for it to have been the product of the Gain-of-Function research on bat coronaviruses in that lab which the NIH began funding in 2014 due to the US-wide ban on Gain-of-Function research that lasted until 2017? [0]

Consider the fact that lab safety protocols are designed to contain pathogens, which creates very poor conditions for viruses to naturally evolve and transfer zoonotically, whereas Gain-of-Function research has the express aim of creating ideal conditions for evolution which is both directed and can proceed many orders of magnitude faster.

*Also, there's plenty of doubt as to whether RaTG13[1] actually exists; we just have the RNA sequence and we're currently just taking Beijing's word for that.

[0] https://www.newsweek.com/dr-fauci-backed-controversial-wuhan... [1] https://www.news-medical.net/news/20200910/Scientists-claim-...

> 1) A disease traveled hundreds of miles to a large city without leaving a trace of evidence

It was certainly circulating in, say, California, for a couple months before it was actually detected [0]. During flu season, seems to me a new respiratory disease can probably get pretty far before anyone notices it's not the flu. It probably crossed the Pacific before it was detected and reported in China, what's a few hundred miles?

All you have to go on are symptoms, and mild/moderate covid doesn't look like anything special, it's not Ebola.

[0] https://www.sfchronicle.com/health/article/First-known-U-S-c...

That story only reports a death-with-COVID that was a few weeks (February 6) before the first-at-the-time discovered community case (February ~26: https://www.ucdavis.edu/coronavirus/news/patient-and-precaut...).

I've seen two people on Twitter claim UCSF personnel have told them COVID was discovered retrospectively in UCSF December 2019 autopsies: https://twitter.com/gojomo/status/1333932912329146368

Neither of the people claiming that seemed to me be prevaricators/hoaxers/people-with-an-axe-to-grind. And, that sort of discovery would be a plausible outcome of a review of all autopsies back to December that California ordered in April – https://talkingpointsmemo.com/news/newsom-orders-all-ca-coun... – on which I've seen little followup reporting. But, I've seen no other confirmation of these UCSF rumors in official statements.

So: still wondering what hard evidence, if any dates COVID-in-the-US to December 2019 or earlier. (There's a survey of December blood donors which found 2% immune reactivity - but the imprecision of that test, especially given known cross-reactivities with other 'common cold' coronaviruses has caused some experts to discount it as definitive proof that COVID was circulating then.)

If you push the first death to Feb 6, then they were probably infected mid-January, and without any known links to China, it seems much more likely than not that there were a cases that percolated around California in December-January before it caused that death:

> “What it means is we had coronavirus circulating in the community much earlier than we had documented and much earlier than we had thought,” said Dr. Sara Cody, Santa Clara County’s public health officer. “Those deaths probably represent many, many more infections. And so there had to be chains of transmission that go back much earlier.”

We're agreed on what's probable, but I'd love to find reliably-reported evidentiary confirmation, especially about magnitude of pre-February-2020 or even 2019 US circulation!

> in the absence of evidence we need to

conclude that we do not know what actually happened.

Coincidences can and do occur, even wildly unlikely ones. Investigating unlikely ones can bear fruit, but condemning on coincidence alone is not wise.

The bio labs definitely warrant a closer look, we just shouldn't jump to conclusions until we've had those looks and collected some direct evidence.

Sadly, it looks like that the Chinese won't let that happen until it's impossible to figure out, either because they have something to hide or because it's just their usual modus operandi.