Thread by @Engineer2The

1/🧵on how did the SARS2 backbone get to Wuhan?

It's pretty well known that the backbone most likely came from SEA, possibly Yunnan, Laos, Thailand, Vietnam, or Cambodia.

2/ A recent publication shows Thailand as center of highest probability and I don't doubt that conclusion.

However, no infections occurred in Thailand till Jan 2020. Why did the virus have to go to Wuhan before travelling back to Thailand?

ncbi.nlm.nih.gov/pmc/articles/P…

3/ A call for more sampling is certainly welcome. However, fur farms operate in Northern China as in the stock picture used from Hengdaohezi, Heilongjiang, China. The cold weather is better for quality fur farming. There's no SARS2 backbone in that area.

nature.com/articles/d4158…

4/ No animals tested positive in Wuhan at the wet market or surrounding area.

"In addition, live SARS-CoV-2 viruses also existed in the environmental samples. However, no SARS-CoV-2 was detected in the animal samples from the market."

researchsquare.com/article/rs-137…

5/ Tian Junhua expanded that search for SARS2 backbone to Jingmen, Xiaogan as well as other areas of Wuhan. No betaCov in raccoon dogs, and no SARS2 backbone in bats.

No SARS2 backbone in Hubei!!

academic.oup.com/ve/article/8/1…

6/ There were low levels of sero-positivity among rural residents in Southern China, as found by EHA. Basically, the in residents in SEA don't have immunity to SARS2 or predecessor.

ncbi.nlm.nih.gov/pmc/articles/P…

7/ The wildlife trade is concentrated in the southern provinces including wild meat and pangolin. There are occasions where wild meat is sold in northern provinces, but this is considered rare compared to the southern provinces.

8/ So how did that SARS2 backbone get to Wuhan?

The fur farms are located in the north, and there's no SARS2 backbone there, so probably didn't originate there. The Backbone likely is in SEA and could have circulated through wildlife trade in the southern provinces.

9/ However, why didn't the epidemic start in Southern China like SARS1? The residents don't have some magical immunity as proved by sero-positivity study. There was no evidence of spillover while travelling the long distance to Wuhan.

10/ In fact, the SARS2 backbone hasn't been found anywhere except bats, humans, and contamination.

Credit to @Daoyu15 for negative everything.

drive.google.com/file/d/13y4XJ_…

11/ The simplest explanation, is SARS2 backbone travelled from South East Asia to Wuhan on an airplane - inside a freezer. What happened after that remains a #drastic mystery.

12/ Bonus: the most logical sample to have travelled from SEA would be Ra4991 from the Mojiang Mine. It didn't have to travel in 2019. It could have made the trip years earlier before being defrosted and fully sequenced.

13/ As for RaTG13, Steven E Massey showed that it's not quite what is advertised.

arxiv.org/abs/2111.09469

14/ "We thus conclude that the hypothesis of the SARS-CoV-2 pandemic being preceded by silent circulation in humans of BANAL-236-like strains leading to the acquisition of a furin cleavage site is unlikely."

So, how did the FCS get there?

researchsquare.com/article/rs-180…