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> In the case of SARS-1 the actual progenitor virus was only found 10 years later in bats in Yunnan. Why do you keep saying this? As you know, the closest anim

> In the case of SARS-1 the actual progenitor virus was only found 10 years later in bats in Yunnan. Why do you keep saying this? As you know, the closest animal viruses to SARS-1 were found in civet cats and raccoon dogs, within about a year of its emergence in humans. The bat viruses that Dr. Shi later discovered are scientifically important, because most of SARS-1's genome probably evolved in bats. They provide no new insight as to how the virus came to infect humans, though.

lamontcg 4y ago
WIV-1 can directly infect humans. So did civit cats and racoon dogs give us SARS-1 or did we infect them (or backwards and forwards as in the case of SARS-CoV-2 and mink)? If you go back a few months before the pandemic outbreak in humans and there's a zoonotic jump to civit cat and raccoon dogs then I don't think you can usefully call that the reservoir species. It existed and evolved for decades in bats, which I'd call the reservoir. The jump to the intermediate animal I'd consider to be part of the pandemic mechanism (unless you can find SARS-1 in samples from a decade previously in those animals). [ And another way to say this is why do we bother calling out an "intermediate species" when discussing pandemics? ]
- tripletao 4y ago
  WIV-1 can infect human cells in vitro. No complete human infected with WIV-1 has ever been identified, living or dead. When SARS-1 emerged in humans, cases were concentrated among traders handling civet cats, as were positive antibody tests. That seems to me like a pretty strong case for forward zoonosis, maybe not perfect but certainly stronger than any evidence we have for SARS-CoV-2. I agree there's no evidence for any animal except bats as the reservoir for SARS-1 (or SARS-CoV-2). The intermediate host seems like the important link to show natural origin, though. Genetic engineers can't invent new viruses de novo, only modify existing ones, so a reservoir host must always exist; the question is just how it got from that reservoir to a human pandemic.
  - sudosysgen 4y ago
    If SARS-1 was more infectious and less virulent you wouldn't see cases concentrated amongst traders, would you? If anything, since many of them already have some kind of immunity from previous infection, you would not expect them to even notice being sick before the virus already infected thousands.
    - tripletao 4y ago
      I agree that finding the origin of a virus that's less deadly and faster-spreading (like SARS-CoV-2) is a harder problem. Nevertheless: 1. We quickly found pretty good evidence (infected civet cats and raccoon dogs, and infected human traders of those animals) that SARS-1 arose from natural zoonosis, within about a year of its emergence in humans. The later discovery of WIV-1 didn't add to this evidence. 2. We've found no such evidence for SARS-CoV-2. That doesn't mean SARS-CoV-2 definitely arose unnaturally--we've expended a lot more effort looking, but it really is a harder problem. It just means we don't know, and we need to keep looking. Do you disagree?
      - lamontcg 4y ago
        They sterilized the market as a containment protocol for SARS-CoV-2, which eliminated the evidence. With SARS-1 the market was still fully operating when they went looking for the origins. Once the human pandemic kicks off and you find some civets or whatever with the virus, then how do you prove they had it before the humans unless you have lucky lab samples drawn from civets who were infected prior to Dec 2019? You'd need to do something like find civit-adapted SARS-CoV-2 which could be genetically dated to prior to Dec 2019 because there were simply too many mutations to have been backspill from the human pandemic. If the spread in civets started very shortly before the spread in humans then that would likely not be possible at this point. If you could find a virus in civets that was 5 years of genetic drift away from SARS-CoV-2 that would probably work, but that may never have existed. What remains is finding the persistent bat reservoir.
        tripletao 4y ago

lamontcg 4y ago

WIV-1 can directly infect humans. So did civit cats and racoon dogs give us SARS-1 or did we infect them (or backwards and forwards as in the case of SARS-CoV-2 and mink)? If you go back a few months before the pandemic outbreak in humans and there's a zoonotic jump to civit cat and raccoon dogs then I don't think you can usefully call that the reservoir species. It existed and evolved for decades in bats, which I'd call the reservoir. The jump to the intermediate animal I'd consider to be part of the pandemic mechanism (unless you can find SARS-1 in samples from a decade previously in those animals). [ And another way to say this is why do we bother calling out an "intermediate species" when discussing pandemics? ]

tripletao 4y ago
WIV-1 can infect human cells in vitro. No complete human infected with WIV-1 has ever been identified, living or dead. When SARS-1 emerged in humans, cases were concentrated among traders handling civet cats, as were positive antibody tests. That seems to me like a pretty strong case for forward zoonosis, maybe not perfect but certainly stronger than any evidence we have for SARS-CoV-2. I agree there's no evidence for any animal except bats as the reservoir for SARS-1 (or SARS-CoV-2). The intermediate host seems like the important link to show natural origin, though. Genetic engineers can't invent new viruses de novo, only modify existing ones, so a reservoir host must always exist; the question is just how it got from that reservoir to a human pandemic.
- sudosysgen 4y ago
  If SARS-1 was more infectious and less virulent you wouldn't see cases concentrated amongst traders, would you? If anything, since many of them already have some kind of immunity from previous infection, you would not expect them to even notice being sick before the virus already infected thousands.
  - tripletao 4y ago
    I agree that finding the origin of a virus that's less deadly and faster-spreading (like SARS-CoV-2) is a harder problem. Nevertheless: 1. We quickly found pretty good evidence (infected civet cats and raccoon dogs, and infected human traders of those animals) that SARS-1 arose from natural zoonosis, within about a year of its emergence in humans. The later discovery of WIV-1 didn't add to this evidence. 2. We've found no such evidence for SARS-CoV-2. That doesn't mean SARS-CoV-2 definitely arose unnaturally--we've expended a lot more effort looking, but it really is a harder problem. It just means we don't know, and we need to keep looking. Do you disagree?
    - lamontcg 4y ago
      They sterilized the market as a containment protocol for SARS-CoV-2, which eliminated the evidence. With SARS-1 the market was still fully operating when they went looking for the origins. Once the human pandemic kicks off and you find some civets or whatever with the virus, then how do you prove they had it before the humans unless you have lucky lab samples drawn from civets who were infected prior to Dec 2019? You'd need to do something like find civit-adapted SARS-CoV-2 which could be genetically dated to prior to Dec 2019 because there were simply too many mutations to have been backspill from the human pandemic. If the spread in civets started very shortly before the spread in humans then that would likely not be possible at this point. If you could find a virus in civets that was 5 years of genetic drift away from SARS-CoV-2 that would probably work, but that may never have existed. What remains is finding the persistent bat reservoir.
      - tripletao 4y ago