In case you didn't know, zoonotic is an infectious disease that can be transmitted between animals. In a recent post, I highlighted Science's paper suggesting that coronavirus originated as a zoonotic virus. It was transmitted from horseshoe bats to other mammals.
Cell has published a new paper that comes to the same conclusion. However, they sum up all of the evidence and not just the phylogenetic (family tree) evidence. However, the new paper isn't as sure about which species of mammal transmitted the virus from bats to humans. They are certain that the virus was not cultured at the Wuhan Institute of Virology, and was then either escaped from the WIV or released to cause disease. Matthew brought this paper to my attention. It features an international team composed of distinguished disease experts. They summarize all evidence that COVID-19 was a purely zoonotic virus and escaped from a Wuhan market and not the WIV. You can download the pdf of the paper by clicking the screenshot below.
Let me just briefly summarize the evidence. There is more to the paper, but the first 11 pages are enough.
1. 1.) These markets are home to high levels of antibodies against different coronaviruses.
2. 2.)
3. 3.) Epidemiologically speaking, the spread of the virus strongly suggests that the source is not the WIV but the Wuhan wet market. The authors point out:
According to epidemiological data, Huanan Market in Wuhan was a major epicenter for SARS-CoV-2. This market sold wild animals and was directly responsible for two of the three oldest documented COVID-19 cases. 28% of all cases reported to WHO in December 2019 were also linked to it (WHO,2021). In December 2019, 55% of all cases were exposed to the Huanan and other markets in Wuhan. These cases were more common in the first half (WHO,2021). The locations of early cases show that the majority of cases are located around the Huanan Market, north of Yangtze River (Figure 1B–E). However, case reporting can be affected by sampling biases due to the density and age structure in central Wuhan. It is not possible to pinpoint the exact location of early cases. These areas were also the first to experience excessive pneumonia deaths in January 2020 (Figure1F-H), which is less vulnerable to biases related to case reporting. The epidemiological link to Wuhan's other locales, including the Wuhan Institute of Virology south of the Yangtze, is not established. This has been the subject of much speculation. Although early cases may not show a direct epidemiological connection to a market (WHO 2021), this is normal given the high rate of asymptomatic transmission (WIV) and undocumented secondary transmission events. This was also observed in Foshan early SARS-CoV cases (Xu et. al. 2004).
If conspiracy theorists claim that the virus was accidentally released from the laboratory, they would have to believe that it somehow made its way to the market before infecting people. The epicenter of the virus was not in the WIV but on the wet market.
4. 4.) The COVID-19 virus was found in environmental samples from the Hunan market. This included the area that sold animal parts and animals.
5. Three Yunnan bat viruses are the closest to the human COVID-19 viruses, as I explained in my post of two days ago. It is still unclear how the relatives or they got to Yunnan's wet market. The truth is that none of these viruses were found by the WIV, and they were all sequenced after the pandemic began.
6. 6.)
7. 7.) You might think that this is the first, but I have other evidence to support this.
8. 8.) There is no evidence to suggest that the WIV, or any other laboratory, was involved in the SARS-CoV-2 virus research or any related virus prior to the pandemic.
9. 9.)
10. 10.) Previous experiments on coronaviruses in WIV included inserting a genetic backbone as well as other genetic markers. We don't see these genetic markers in the COVID-19 human virus that is causing the pandemic.
11. Workers would need to infect wild-type animals in order to culture the virus in a laboratory. However, they were unable do so using SARS-CoV-2. Although the virus was able to be cultured in mice after the pandemic, it was not yet available for human use.
12. 12.)
13. 13.) They may be absent in coronavirus close relatives. This could simply reflect our profound ignorance about the origins of SARS-CoV-2. There is no evidence to suggest that such genetic engineering took place at WIV.
Conclusions on pages. Conclusions on pp.
The most unlikely explanation for SARS-CoV-2's origin is a zoonotic event that involves transfer from an intermediate host to a Wuhan market. SARS-CoV-2 does not appear to have a laboratory origin.
The last paragraph:
Although the source of SARS-CoV-2 virus in animals has not been identified, and key species may not be tested, there is ample scientific evidence that supports a zoonotic origin. Although the possibility of a laboratory incident is possible and it may not be easy to falsify the results, it is unlikely that this channel for emergence would occur given the number and frequency of human-animal interactions in the wildlife trade. If we fail to thoroughly investigate the zoonotic origin of the virus through coordinated and collaborative studies, the world could be vulnerable to new pandemics that arise from the same human activities which have repeatedly placed us in a collision course to develop novel viruses.
Although this paper is tentative as with all such conclusions, the data point up to a normal, zoonotic event, and not an escape from the laboratory. The virus was not designed to kill humans, and there is no evidence that it was created by the WIV. Even if it had, how could it have managed to escape to wet markets where such viruses are naturally found? There is no evidence to suggest that the WIV was not studying the virus, but that it accidentally escaped causing the pandemic.
In other words conspiracy theories about the virus appear to be unfounded, but humans are human and are prone to conspiracies so they'll continue to persist.
UPDATE: In the thread that follows this tweet, Rasmussen, a third author, reviews the evidence people believe supports a lab origin and then disproves it.
Our review of evidence regarding the origins SARS-CoV-2 has moved from a preprint to peer-reviewed proof in @CellCellPress. Can we rule out a "lab leaked"? No, but if we objectively follow the evidence, it leads us away from that hypothesis.https://t.co/IF2jAZ7BQE Dr. Angela Rasmussen (@angie_rasmussen) August 19, 2021
Matthew
