There has been a debate about the origin of the COVID-19 outbreak, with two main theories being that it was a spillover event from wild animals or a leak from the nearby wet market. There were accusations that the virus was deliberately engineered and released from the lab, but there was a strong argument against it being genetically modified. There was debate on this topic, but eventually a consensus was reached that the virus is not engineered. The lab-created hypothesis was replaced with the lab-leak hypothesis, which states that the virus was spread from the lab to the community.
Unfortunately, this important scientific question became the focus of politics, with many in the public holding opinions not based on the status of the scientific evidence but their political loyalties. The research has moved in a certain direction.
There are many types of evidence that can be brought to bear. There are activities and events occurring in the lab and market. Teams have been investigating the lab. They haven't been able to rule out the lab-leak hypothesis completely, but they are still looking into it. China has been less than cooperative, and they are very defensive about the lab-leak theory, which they see as blaming them for the epidemic. The lab-leak idea is alive and well due to this.
The genetics of the virus are another line of evidence. This has largely ruled out the idea that the virus was modified. It supports the idea that the virus came from animal populations and then spread to humans. This type of examination did not find the "smoking gun" of the new form of the virus. It is not surprising that this does not call into question the animal spillover hypothesis. American minks, red foxes, and raccoon dogs are some of the animals that can be used as intermediate hosts for SARS- CoV-2.
Epidemiology is the third type of evidence we can use to address this question. The evidence shows that both the wet market and the lab are in the city of Wuhan. We needed to know more about the two hypotheses. There are two studies that argue for the wet market theory.
The first study used genetic analysis to find out where the virus came from. Genetics can be used to trace the spread of the virus as it splits off into different types. The analysis shows that there were two separate spillover events in late November and early December of 2019. The authors have come to a conclusion.
These findings indicate that it is unlikely that SARS-CoV-2 circulated widely in humans prior to November 2019 and define the narrow window between when SARS-CoV-2 first jumped into humans and when the first cases of COVID-19 were reported. As with other coronaviruses, SARS-CoV-2 emergence likely resulted from multiple zoonotic events.
There is a lab leak hypothesis. The knockout punch was delivered by the second study. They looked at environmental samples to see where the virus may have been at the time. They were able to find it.
We report that live SARS-CoV-2 susceptible mammals were sold at the market in late 2019 and, within the market, SARS-CoV-2-positive environmental samples were spatially associated with vendors selling live mammals. While there is insufficient evidence to define upstream events, and exact circumstances remain obscure, our analyses indicate that the emergence of SARS-CoV-2 occurred via the live wildlife trade in China, and show that the Huanan market was the epicenter of the COVID-19 pandemic.
The first cases may have occurred in the market. The data was characterized this way.
“In a city covering more than 3,000 sq miles (7,770 sq km), the area with the highest probability of containing the home of someone who had one of the earliest Covid-19 cases in the world was an area of a few city blocks, with the Huanan market smack dab inside it.”
You can see the data visually from the main image. The lab-leak hypothesis can't be aligned with this data. You would have to think that there were two lab-leak events, one of which went to the Huanan market and the other to the other. It is not sound epidemiological reasoning.
The lab-leak hypothesis is no longer valid. The conclusion that COVID resulted from spillover events in the Huanan market is a fairly solid one. It's important to understand as it relates to our efforts to prevent future spillover events. There were more than 47,000 individual live animals from 38 different species sold in the Huanan market in the last two years. The conditions were unsanitary. The kind of close contact between animals and humans is related to zoonotic events.
Steven Novella is the founder and currently Executive Editor of Science-Based Medicine. The Great Courses and The Skeptics Guide to the Universe were both written by Dr. Novella.
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