"No convincing natural zoonotic origin for the pandemic will ever be found by China or the WHO or anyone else – for the simple reason that one does not exist" – scientists
Here's an excerpt from an excellent article that points out that the chances that SARS-CoV-2 has a zoonotic origin are vanishingly small.
Why China and the WHO will never find a zoonotic origin for the COVID-19 pandemic virus
by Jonathan Latham, PhD and Allison Wilson, PhD
Independent Science News, 16 Feb 2021
[links to sources at this URL]
In China there is a popular joke about the southern city of Guangzhou (Canton). A visiting space alien, curious to learn about Chinese customs, tours its various provinces. Arriving in Guangzhou the alien asks the locals what their interests are. The Cantonese oblige their guest by putting the alien in a soup pot and eating it. This joke hinges on the Cantonese fondness for cooking with unusual species, many obtained from far away.
This feature of Canton’s cuisine was implicated in the original SARS (Severe Acquired Respiratory Syndrome) pandemic of 2002-04, which began in Guangzhou. It is thought that the virus arrived there with palm civets imported for speciality dishes (Wang et al., 2005).
But this culinary connection also marks a defining difference between the first SARS coronavirus pandemic and the current one. The COVID-19 (SARS-CoV-2) pandemic began in Wuhan, but Wuhan was considered a comparatively unlikely location for a natural (zoonotic) coronavirus spillover (Yu et al., 2019). It has no cultural or geographic or climatic predisposing factors.
For example, being fairly far north, bats are not abundant in Wuhan and Hubei province has few bat coronaviruses compared to hotspots like Yunnan and Guangdong (Yu et al., 2019). Unlike Canton, Wuhan is not famous for exotic fare. Nor is Wuhan near animal smuggling and trading origins (Li et al. 2019). It was for this reason that researchers from the Wuhan Institute of Virology (the WIV), which is the prime suspect in the various lab leak theories, mostly had to travel thousands of kilometres to find bats with coronaviruses (Yu et al., 2019). Furthermore, when WIV researchers needed to study a Chinese population that was not routinely exposed to bat coronaviruses (as a control group), they chose Wuhan residents (Wang et al. 2018; Li et al. 2019).
It is consequently a mystery, if SARS-CoV-2 does have a zoonotic origin, why COVID-19 should have emerged where it did. As Zheng-li Shi, head of coronavirus research at the WIV told Scientific American, in March 2020: “I had never expected this kind of thing to happen in Wuhan, in central China”.
What is the probability of a natural zoonotic coronavirus outbreak starting in Wuhan?
It is possible, and potentially helpful, to put numbers on Zheng-li Shi’s surprise. Numbers can more precisely show the incongruity of an outbreak occurring in Wuhan. But before using them it is important to specify the assumptions required so that these numbers can be treated with appropriate caution.
Such a calculation requires that we set aside momentarily all the varied, potentially important, but hard-to-quantify-and-mostly-unknown local factors, like those mentioned above, that may make certain locations or populations less or more likely to originate a pandemic. (For a broader discussion of these factors see e.g. Graham et al., 2013)
Given these provisos, and knowing that (1) bats and other animals which harbour coronaviruses are found practically all over the world, and (2) that the population of Wuhan is 11 million, and that (3) the global population is 7 billion, we can calculate the likelihood of Wuhan being the epicentre of a natural zoonotic coronavirus pandemic: The chance of a person from Wuhan being patient zero is approximately 630-1.
Therefore, if we were Zheng-li Shi, we would have “never expected” a natural zoonotic outbreak in Wuhan either. Imagine her surprise, and that of her colleagues when, in December 2019, they learned of a local coronavirus outbreak. They (and other researchers) travel all over the world, and not just China, looking for coronaviruses yet a pandemic breaks out in Wuhan, under their very noses. It truly is, very, very, unlikely that a natural zoonotic pandemic would start in Wuhan. Yet no commentator on the outbreak seems to have properly acknowledged the true scale of this improbability.
The second coincidence is an evolutionary coincidence
But there is, in fact, a second coincidence regarding the origin of the COVID19 pandemic. This coincidence has seemingly been entirely disregarded; but it too points strongly to a lab origin. The underlying logic is quite simple and it has to do with the evolution of coronaviruses.
Zheng-li Shi’s laboratory at the WIV is a world centre of coronavirus research. This has been mentioned often and is widely known. In particular, the Wuhan Institute of Virology is a world-leading site for bat coronavirus collection (and the virus came from a bat). But what has not been foregrounded is that, even within the coronaviruses, Zheng-li Shi’s laboratory had, of the 28 relevant coronavirus species, singled out just one of them as their special focus. And it is a member of this species (called the “SARS-related coronaviruses“) that broke out in Wuhan in 2019.
This, then, is a further curious coincidence: for a pandemic coronavirus (SARS-CoV-2) to emerge in Wuhan and be a member of the species most studied at the Wuhan Institute of Virology.
The logic of coronavirus pandemics
A fuller appreciation of this coincidence requires visualising coronavirus evolution and understanding the research agenda at the WIV.
The coronaviruses are divided into four types: Alpha-, Beta-, Gamma- and Delta- coronaviruses. These are shown in Fig. 1 which is a phylogenetic (evolutionary) tree adapted from a paper by Li et al., 2020. (The print is small and so here is a link to the original figure.)