Thread by @Ayjchan

Is there evidence that definitively supports SARS2 spilling over from animal to human at a market?

There is none. Existing evidence is consistent with a person bringing SARS2 into Huanan Seafood Market, resulting in a cluster of cases.

Yet, a 2-market hypothesis has emerged...

At least one virologist has repeatedly suggested that SARS2 spilled over not only once but twice in Wuhan city at different markets.

Why? Because at least one of the earliest SARS2 lineages was not observed among Huanan cases.

There are 2 major problems with this hypothesis.

1. The 2 early lineages (the one found in Huanan cases, and the other not found in Huanan cases) only differ by 2 letters out of 29.9K letters. It's much more likely SARS2 was introduced 1 time into humans.

https://twitter.com/trvrb/status/1408080716286414852

2. The other market, associated with the 1st confirmed Covid-19 patient (reportedly), is an RT-mart, a hypermarket aka supermarket + department store. Kind of like a Costco. I think safe to say live mammals not sold there.
h/t @rowanjacobsen
Page 178 China-WHO joint study annex

This is not to say that it is impossible for SARS2 to have spilled over naturally in Wuhan city or Hubei Province.

A recently published study showed that, contrary to what the WHO experts were told (even by witnesses), wild animals were traded in Wuhan.
nature.com/articles/s4159…

It has just become apparent, over time, that there is an absence of evidence pointing to a spillover event at Huanan Seafood Market; although in early 2020 it was widely reported that the virus had likely come from illegally traded wildlife at the market.
newsweek.com/wuhan-seafood-…

I think it's important to nip the 2-market hypothesis in the bud before it appears in a reputable news article... like the misinformation that there are SARS2-like viruses frequently spilling over into people in Hubei/Wuhan.

https://twitter.com/Ayjchan/status/1404885216251072512

I believe that both natural and lab origin hypotheses should be investigated properly.

This means gathering evidence and info relevant to the presence of potential animal hosts in Wuhan/Hubei... not ransacking their equivalent of a Costco or the city's cold storage facilities.

This also means getting a handle on who the first covid-19 patients in Wuhan were and where they had been in the 2 weeks prior to developing symptoms.

Unfortunately, it has been difficult to find out. The China-WHO study claims the 1st case only developed symptoms on 8 Dec 2019.

I'm trying to understand why Chinese scientists (without any international help) were able to so swiftly track down early cases + intermediate hosts for SARS both times it spilled over in 2002-2004. But in 2019, despite much improved tech, could not find potential animal hosts.

If the 2-market hypothesis is true, that means that not only 1 but 2 pools of animal hosts of the super infectious and transmissible virus vanished.

Another hypothesis is that the swine flu outbreak in 2019 caused Chinese people to hunt and eat more wildlife than normal due to higher pork prices.

For this, I'd like to point everyone back to the recently published study on wild animals sold in Wuhan. theguardian.com/environment/20…

"Regarding our insights into broader IWT issues in Wuhan, the animals sold were relatively expensive, representing luxury food items"

Would higher pork prices have led to increased demand of luxury exotic meats?? Instead of regular 🐮🐔🐑 livestock?
nature.com/articles/s4159…

It doesn't make sense that if the price of pork goes up, large numbers of people will then decide to pay 10x the price to make fried rice or dumplings with exotic meat they're not familiar with.

So I don't find the swine flu > increased spillover hypothesis convincing.