Thread by @Ayjchan

In this @Medium post, I counter the claim that there is a substantial body of evidence pointing to a natural origin of COVID-19.

All publicly available evidence and information are consistent with both natural and laboratory origin scenarios.
ayjchan.medium.com/a-response-to-…

Only with more data and information can scientists confidently evaluate the likelihood of each origin hypothesis.

A credible, transparent, evidence-based, and international investigation of the origin of Covid-19 is not only vital but also feasible.

Key points:
1. The 2003 epidemic SARS-CoV was quickly traced to proximal animal sources of the virus. Yet, despite greatly improved surveillance technologies and capabilities, an intermediate host for SARS-CoV-2 has still not been found more than 1.5 years.

Setting aside challenges verifying early case data...
2. Geographic distribution of early cases by home address overlaps with densely populated Wuhan districts with higher proportions of the elderly - a plausible alternative explanation to the location of the seafood market.

3. The identification of early cases may have suffered from ascertainment bias because one of the criteria used initially to determine cases was exposure to the Huanan seafood market and related markets. See Annex E3 of the China-WHO joint report.
who.int/publications/i…

4. The fact that the home addresses of early cases are not concentrated close to WIV campuses is a weak argument. Previous natural spillovers and lab escapes illustrate the importance of tracking down early patients and identifying their exposures to various possible sources.

5. Furin cleavage sites exist in other coronaviruses, but have not been found in sarbecoviruses. Despite the discovery of a growing number of close virus relatives of SARS-CoV-2, an S1/S2 FCS insertion remains unique to SARS-CoV-2.

6. We have little insight into the viruses and virus sequences available to scientists and the experiments being conducted in labs prior to the Covid-19 outbreak. Varied cell types were used to culture viruses...

... It is premature to predict what sequences may have been engineered or that the cells used would have selected against furin cleavage sites.

On the multi-market hypothesis...
7. The existing genetic and epidemiological data point to a single introduction of SARS-CoV-2 into humans. An origin hypothesis involving multiple spillovers from animals to humans at multiple locations is not parsimonious...

... especially given that there is still no direct evidence for spillover at even a single market. Not to mention multiple markets.

How large would the cover-up need to be to conceal animal sources of the virus at multiple markets?

8. Mutation of SARS2 during pandemic does not contradict hypothesis that it was pre-adapted to human infection in Dec 2019. Both SARS1 and SARS2 are generalist viruses. If 2003 SARS epidemic had been allowed to expand to millions of cases, recurrent mutations would be observed.

9. Plausible lab origin scenarios were not addressed by either the Proximal Origin correspondence or the recent Holmes et al. critical review that focused on straw men scenarios. The available data and information remain consistent with both natural and lab origin hypotheses.

Importantly, if the argument for the lack of direct evidence for a natural origin is that not enough animals have been tested, then one should apply the same standards to evaluating lab origin scenarios and advocate for access to relevant samples, data, and information.

Addressing the market spillover hypothesis directly, these questions remain unanswered:

1. What animals were on sale in Wuhan markets in the winter of 2019? Were the 457 animal samples from the Huanan seafood market representative of these animals on sale in the winter of 2019?

2. Why were farms that supplied wild animals to Wuhan shut down without testing for the virus to definitively track down the source?

It is in China's own national security interest and well within their abilities to pin down the source of a killer virus.
wsj.com/articles/covid…

3. In the absence of any animal samples positive for the virus, what is the evidence of an intermediate host?

80,000+ wildlife, livestock, and poultry samples were collected from 31 provinces in China. 41,696 were wild animal samples.

No signs of SARS2 found.

In other words, there is zero evidence that animal sellers at the Huanan seafood market had been frequently exposed to animals carrying SARSr-CoVs or that natural spillovers of SARSr-CoVs would be expected in Wuhan prior to the emergence of SARS-CoV-2.

On the other hand, we know some of the work at the WIV is classified.

In November 2019, students working on classified topics were told that their papers may not be published publicly. Some research reports could be sealed for up to two decades.
washingtonpost.com/world/asia_pac…

Not all research and newly discovered viruses are published in a timely manner or, in some cases, at all.

For instance, eight SARSr-CoVs collected by the WIV in 2015 from the Yunnan mine with the sick miners were only revealed to the public in 2020.

https://twitter.com/Ayjchan/status/1397593464079015946

To rule out lab origin hypotheses, it will be at minimum necessary to know what samples WIV had collected from animals and humans (where and when) and obtain access to the currently missing WIV pathogen database that was taken offline in September 2019. washingtonpost.com/opinions/2021/…

Gaining access to comprehensive Wuhan research and personnel records and being able to confidentially interview relevant individuals through a safe whistleblower mechanism would boost confidence in an investigation of possible lab origins.

Because we know so little about what was happening in labs prior to Covid-19, we cannot dismiss the possibility that the virus may have been cultured, manipulated, and even engineered or recombined in the laboratory without leaving obvious signs of human interference.

Because we still know so little about early cases, proximal animal sources and research activities involving SARSrCoVs prior to the pandemic, we must rigorously investigate all plausible natural and laboratory origin hypotheses to prevent future pandemics. pnas.org/content/117/47…