Bit of news came out last week about the origin of SARS-CoV-2. I'm going to go over the science of that, but there's also a complicated story about where the evidence came from that's noteworthy, but I'll get to that second.
In the absence of any evidence, the more probable hypothesis would have to be considered a jump from animals to humans, given that it's happened so many times in the past: Ebola, various flu strains, HIV, and at least two different coronavirus strains (MERS and SARS-1). Viruses have escaped from labs a couple of times in the past, but it's pretty rare, and the viruses have always been well known prior to the escape. That's just a matter of probability - more people work on common viruses, so there's simply more opportunity for one of those to escape.
For a natural origin, suspicion has focused on a market in Wuhan that is known to have had live animals present (though the Chinese authorities would tell you otherwise). A paper in Science later provided strong evidence linking the origin of the pandemic to the market. Basically, all the early cases occurred in tight physical proximity to the market. Genomic information also indicates that there were two initial strains that jumped to humans, and both were centered on the market. That's highly suggestive of the virus spreading within the market before making the transition to a new species.
You can, potentially, imagine scenarios where there was someone who worked in the lab and lived near the market and incubated the virus long enough for it to evolve into distinct strains, but those scenarios start to get convoluted very quickly, and so are less likely.
The new information, confirmed last week by the WHO, is that a large set of environmental DNA* was sequenced from the market, and those showed the presence of SARS-CoV-2 there early in the pandemic, and that it was consistently associated with DNA from raccoon dogs. That species is both known to have been present in the market, and confirmed to be susceptible to infection by the virus. So this is more evidence that's consistent with an origin among the animals at the Wuhan market.
But again, this is not decisive - you can still imagine scenarios where someone carried an infection from a lab and managed to infect the raccoon dogs at the market without causing widespread human infections. But that's getting even more improbable.
So, that's the science. The background on this information has to do with the fact that this information is coming out over three years after the data was gathered. It turns out that all the environmental sampling data was put up on a Chinese server shortly after it was gathered, then was pulled back down shortly afterwards. It's not clear if it was pulled down because the Chinese government didn't want to acknowledge that it showed it was hosting a live animal market that trafficked in endangered species and ordered the researchers to delete it, or because the researchers decided that they might get in trouble for sharing it and pulled it ahead of anyone noticing.
Regardless of why it got pulled, it was too late. Someone outside of China grabbed a copy of it. But why they waited to do anything with it isn't clear. Maybe they forgot they had it/didn't realize its importance, maybe they knew researchers in China and didn't want to get them in trouble, maybe something else. There's an account of some of the strange behavior, but it feels very incomplete.
Anyway, at this point, there's a paper on the sequences in peer review, so nobody involved with the work is saying much until it's set to be published. We'll probably learn more within a few months.
* The SARS-CoV-2 genome is RNA, so had to be converted enzymatically to DNA. So the data's actually a mix of DNA and RNA sequences.
In the absence of any evidence, the more probable hypothesis would have to be considered a jump from animals to humans, given that it's happened so many times in the past: Ebola, various flu strains, HIV, and at least two different coronavirus strains (MERS and SARS-1). Viruses have escaped from labs a couple of times in the past, but it's pretty rare, and the viruses have always been well known prior to the escape. That's just a matter of probability - more people work on common viruses, so there's simply more opportunity for one of those to escape.
For a natural origin, suspicion has focused on a market in Wuhan that is known to have had live animals present (though the Chinese authorities would tell you otherwise). A paper in Science later provided strong evidence linking the origin of the pandemic to the market. Basically, all the early cases occurred in tight physical proximity to the market. Genomic information also indicates that there were two initial strains that jumped to humans, and both were centered on the market. That's highly suggestive of the virus spreading within the market before making the transition to a new species.
You can, potentially, imagine scenarios where there was someone who worked in the lab and lived near the market and incubated the virus long enough for it to evolve into distinct strains, but those scenarios start to get convoluted very quickly, and so are less likely.
The new information, confirmed last week by the WHO, is that a large set of environmental DNA* was sequenced from the market, and those showed the presence of SARS-CoV-2 there early in the pandemic, and that it was consistently associated with DNA from raccoon dogs. That species is both known to have been present in the market, and confirmed to be susceptible to infection by the virus. So this is more evidence that's consistent with an origin among the animals at the Wuhan market.
But again, this is not decisive - you can still imagine scenarios where someone carried an infection from a lab and managed to infect the raccoon dogs at the market without causing widespread human infections. But that's getting even more improbable.
So, that's the science. The background on this information has to do with the fact that this information is coming out over three years after the data was gathered. It turns out that all the environmental sampling data was put up on a Chinese server shortly after it was gathered, then was pulled back down shortly afterwards. It's not clear if it was pulled down because the Chinese government didn't want to acknowledge that it showed it was hosting a live animal market that trafficked in endangered species and ordered the researchers to delete it, or because the researchers decided that they might get in trouble for sharing it and pulled it ahead of anyone noticing.
Regardless of why it got pulled, it was too late. Someone outside of China grabbed a copy of it. But why they waited to do anything with it isn't clear. Maybe they forgot they had it/didn't realize its importance, maybe they knew researchers in China and didn't want to get them in trouble, maybe something else. There's an account of some of the strange behavior, but it feels very incomplete.
Anyway, at this point, there's a paper on the sequences in peer review, so nobody involved with the work is saying much until it's set to be published. We'll probably learn more within a few months.
* The SARS-CoV-2 genome is RNA, so had to be converted enzymatically to DNA. So the data's actually a mix of DNA and RNA sequences.
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