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1/It looks like the “leaked from a lab” conspiracy theory is lighting up again, so I’m going to go over a bit of what we know about the origins of SARS-CoV-2 and why it’s unlikely that it leaked from a laboratory in China. (Viros/epis, feel free to chime in)
2/When the pandemic broke in Wuhan, and it came out that there’s a prominent bat coronavirus virology laboratory also in Wuhan, it seemed like too huge a coincidence not to be connected. Wuhan is a great distance from the known natural reservoirs of SARS-like bat coronaviruses.
3/It turns out that the scientist who runs that lab, Shi Zhengli, had the same terrible thought when she first heard the new pneumonia was caused by a coronavirus. As reported in Scientific American, Shi checked sequences of their lab viruses and found no matches, no mishandling.
4/Of course, there’s another theory going around, and I thought of this, too. What if one or more of the lab workers were exposed to the virus in the field, unknowingly, and set off the pandemic in Wuhan?
5/Shi addressed those concerns in an interview for Science last summer, stressing that her lab meets strict BSL3 standards and no one has tested positive for antibodies. https://science.sciencemag.org/content/369/6503/487
6/And the thing is, this theory that a lab worker was patient zero reduces to “what if a person caught it from a bat?” which, well, is the whole point. Yes, we are pretty sure a person caught it from a bat. But it could be any of thousands or millions living/working nearby.
7/One clue is a serosurvey carried out by Shi’s group and published in 2018 from people who live in the area of Shitou cave, a natural reservoir of SARS-like viruses (not COVID-19). And they found 6 people, or 3% of their group, had antibodies. https://link.springer.com/article/10.1007/s12250-018-0012-7
8/These are people who had not handled any wildlife or had any pneumonia symptoms. This strongly suggests that human exposure to bat coronaviruses is a common event, not a rare event.
9/There’s still the problem of how did the virus travel 1000 miles to spark an epidemic in Wuhan, if not carried by someone, like a bat scientist, who traveled there and back?
10/This is only a coincidence if you’re sure that the epidemic actually started in Wuhan. Early phylogenetic studies of the SARS-CoV-2 genome found three early variants, named A, B, and C, with A being the ancestral type. https://www.pnas.org/content/117/17/9241
11/Variant B was the dominant variant during the Wuhan outbreak. The A type was found in four Chinese individuals from Guangdong, and in 3 Japanese and 2 American patients.
12/If SARS-CoV-2 didn’t even start originally in Wuhan, but only blew up there after the virus made the jump to humans elsewhere, there’s no longer a coincidence at all to cast suspicion on the Wuhan Institute of Virology.
13/In conclusion, while one can’t 100% rule out some kind of lab leak, the most likely scenario is it was a completely common and unremarkable transfer from bat to human, which happens all of the time.
14/More importantly, we must learn lessons from this pandemic so it doesn’t happen again. The scientific community is rightly debating the safety of “gain of function” research. But we can’t overlook the much greater risk of viruses jumping during casual contact with wildlife.
15/And while trying to cast blame at one lab or one scientist, we are ignoring the gigantic, worldwide experiment of a largely uncontrolled virus spreading and mutating among humans and among mink, which has already produced multiple highly transmissible variants. END
