[orwin]

I agree with you for the begining, but this part:

> The fact that the entire clade has a root in October 2019 (and we can see this even because the first viruses sequenced differed by only one or two mutations from their common ancestor) indicates that there was not slow community spread before the initiation of the pandemic period. There is no weaker progenitor virus.

is hard for me to understand.

Rural China in not rural USA. At all. I've hiked for a month in the Appalachian, another one in the Sierras, and spent two month in rural China. Rural china is as i used to imagine rural Africa.

Rural china have two particularities: young, probably younger than you imagine. You have villages with a median age of 15, with no middle-aged inhabitants. And enclaved. You have villages where you have to use a jeep (that the village do not own) to get to.

Is it possible, in you opinion, to have an early SRAS-Cov2 infecting a village, festing on the people for weeks or even months, then a parent coming back for his yearly vacations, getting infected, then going back to work in Wuhan?

I'm not a biologist, so i don't understand how viruses works, but i _know_ rural China (and rural europe, and rural USA.)

[inciampati]

This process would leave traces that we would have detected by now. If this happened, we should see viruses that sit outside the Wuhan-rooted SARS-CoV-2 clade but are otherwise the same. The rate that this happens would be low, but it would have been observed. I would expect that the epidemic required to spread from rural to urban regions would be large enough to throw off daughter strains that would have been circulating after the main outbreak was discovered. These would have been detected by the mobilization to find the origins and scope of the pandemic. Of course we can make stories about a perfect chain of transmission leading from a bat cave in southwest China to a major population center, where each step never resulted in obvious illness or community spread. I also enjoy science fiction. Some things make for nice stories but involve staggeringly improbable series of coincidences. And if the same virus (remember: thanks to it's error correcting mechanisms it doesn't change very fast) were let loose in another community, why would it not take up residence there? We would have to explain why people in Wuhan and the rest of the world were so much more susceptible to a virus that was completely wiped out along it's entire chain of transmission from probable animal host to human.

[orwin]

>> Of course we can make stories about a perfect chain of transmission leading from a bat cave in southwest China to a major population center, where each step never resulted in obvious illness or community spread. I also enjoy science fiction.

Yes, the part "where each step never resulted in obvious illness or community spread" is where i don't understand. I think i insisted on it enough, but it bears repetition: rural china is _young_ and _enclaved_. I've seen villages with 70 children, 10 adults total. Granted, the adults are "old" (i understand they are between 40 and 60, the life expectancy is not that high). You also have phantom villages. If you ever read Lord of the Flies, you can imagine how a village get abandonned and trashed.

How it works: people get kids early, did not declare them, go to work in the city and let the kids for the remaining farmers (often village chiefs and to ones speaking Mandarin, all the other speak in local dialects) and sometime grandparent. Few of the young adults stay (women that were "shamed" into staying from what i understood, the guide was not very proud and did not expand on this). Most of them come back either once or twice a year, sometime more if they work closer, but not more than once a month. Couples sometime come back to drop a kid or two in the village before going to work again.

> And if the same virus (remember: thanks to it's error correcting mechanisms it doesn't change very fast) were let loose in another community, why would it not take up residence there?

And if he did take residence, how would we know? If a 100-person village was infected, they would be immune by now. If only one external (or even ten, most asymptomatics don't transmit the virus if i understand that well) was infected and transmitted the virus directly in Wuhan, would it be possible?

One more fact: some parts of rural china are way less connected than western Africa. I did not visit Africa yet (my next month-long hike was supposed to be in Ethiopia, stopped for obvious reasons), but the preparation are less stringent, and the path easy to plot. I guess western Africa, with less mountains/hills, would be even more connected.

You see, i agree that a chimera might have escaped, is a possibility that i find more likely (let's say 45 to 80%, depending on the day). But as long as proponents of this theory dismiss the other theories as "science fiction" _when they view rural China as rural Europe_, i will have a bad time getting onboard the theory.

I'm not skeptic of everything, but still, the 2000's outbreak of BDBV or all those novel-ebola where we never find the index case nor the origin village, why couldn't they have been lab outbreak too? There is research in the area, they have to keep Chimeras for some of the EV because else they can't keep those new versions alive long enough, i'm pretty sure there is less security (i imagine, i don't know Africa very well). Were those ebola viruses with no index case lab outbreaks too? Why didn't we talk about it ever?

[bhickey]

HIV is believed to have first infected humans in the 1920s where it traveled up the Congo before arriving in Kinshasa. From there it radiated across Africa carried by truckers. Like you say, I haven't seen evidence to rule out rural circulation before arriving in Wuhan. Granted, I don't think this is the most likely series of events, but the GoF lab leak hypothesis is lacking support.

[tim333]

The documents that the article is based on demonstrate the lab was doing GoF experiments to infect humanized mice with chimeras based on bat coronaviruses and got a grant to do further such research starting in 2019. And lo - we get a break out of something looking like a bat based chimera that infects human cells in 2019. Bit of a coincidence there.