COVID-19 is the most significant pandemic that almost everyone alive today has lived through, and yet we are still not completely sure about its origins. There is no smoking gun by which we can definitively trace the origins of the SARS-CoV-2 virus that causes COVID. Recent statements by US government officials has reignited the debate about its origins, a topic we have covered here extensively.

SARS-CoV-2 is a novel virus, so it had to come from somewhere. Scientific papers were published as early as March 2020 exploring this question. There have always been two major hypothesis, what we now call the “lab leak” hypothesis, and the “spillover” hypothesis. Unfortunately this has not been a pure scientific debate as politics has intruded from the beginning. China in particular objects to any suggestion that their lab in Wuhan caused the worst pandemic in a century.

It is worth pointing out, however, that the lab leak theory has its origins in a lab-created bioweapon theory. Very early on, and continuing at least through 2022, some scientists and others were hypothesizing that the virus was bioengineered as a weapon, which may then have either been deliberately or accidentally released. This question can be primarily answered by examining the virus itself, looking for telltale signs of bioengineering. The book is basically closed on this question – the evidence strongly supports a natural (not bioengineered) origin for the virus.

Once the evidence was moving strongly in the direction of a natural origin for the virus, further promotion of the idea that it was bioengineered took on strong conspiratorial tones. Such conspiracy theories were widely criticized (correctly so). However, the bioweapon hypothesis soon became replaced by the lab leak hypothesis – in this narrative the Wuhan lab was just studying (but not modifying) the SARS-CoV-2 virus when it accidentally was leaked from the lab, likely through infected lab workers. The lab leak hypothesis was compatible with the growing evidence for a non-bioengineered origin of the virus.

It seems that some of the bioengineered conspiracy theorists migrated over to the lab leak hypothesis, contaminating the debate with conspiracy theories. Meanwhile earnest proponents of the lab leak hypothesis bristle at any suggestion that they are conspiracy theorists. Fair enough – but they have to understand the history and recognize that the lab leak side is rife with conspiracy theories.

If we put all that aside and just take a look at the scientific question – what does the evidence say about the origin of SARS-CoV-2 – there are basically two ways to address the question. The first stems from virology, tracing the genetic sequence of the various strains of SARS-CoV-2 and trying to draw the lines back to its origin. We can also compare the genetic sequence to the most closely related viruses to try to piece together where the virus came from.

When we do this the evidence currently favors the interpretation that SARS-CoV-2 is a spillover virus, a coronavirus that infects animals that crossed over to humans either through mutations or combining genetic material from human-infecting viruses in order to be pathogenic against humans. The best animal candidates for hosts of the virus origin are minks, red foxes, and racoon dogs, all of which are sold in the Wuhan wet market. Epidemiological evidence also traces the first infections back to the wet market. For this reason this is the most popular hypothesis among scientists. However, we have still not found the smoking gun original virus, so there is still a little room for questions.

The second way of approaching the question of the origin of the virus is to investigate the Wuhan virology lab and China’s early handling of the outbreak. This is more akin to a detective investigation than a scientific study. The World Health Organization and the US government have both executed these types of investigations, and their results are equivocal. They say, essentially, that there is no evidence for a lab leak but China has not been transparent enough for the lab leak hypothesis to be definitively ruled out.

This is the situation we have been living with for about the past year. Individuals can defend whichever hypothesis they prefer by emphasizing whichever aspect of the evidence they choose. For example, those who favor the lab leak hypothesis can argue that China would have not reason to be cagey unless they were hiding something. This is a weak argument, in my opinion, because authoritarian governments are cagey by design. I find the scientific evidence more compelling that the equivocal investigative evidence. Just following this evidence and expert opinion, I think the best current summary is that the evidence strongly favors the spillover origin hypothesis, but there is still some small room for doubt, and of course we should be open to more evidence. This will essentially remain the case unless and until scientists do find the actual host species and virus of origin for SARS-CoV-2, but that may never happen.

The lab leak hypothesis is back in the news not because of any new scientific evidence, but because Christopher Wray, Director of the FBI, has now publicly said that:

“The FBI has for quite some time now assessed that the origins of the pandemic are most likely a potential lab incident,”

In response the White House put out a statement saying that there is no consensus among the various federal agencies as to the origin of SARS-CoV-2. It is not surprising that an investigative body would favor investigative evidence, while scientific bodies favor scientific evidence. Also, while the science is completely transparent, the FBI chief can only refer to classified information. So while I, of course, cannot know anything about any alleged classified information, Wray did emphasize in his interview that China “has been doing its best to try to thwart and obfuscate” their investigation. So it seems his reasoning is similar to what we already had – China is being cagey.

Intelligence agencies are divided on their conclusions, while scientific institutions are more united. In the end I don’t think Wray’s statements change anything. I would still favor the spillover hypothesis based on the scientific evidence, and the lack of any firm investigative conclusion. But of course I also favor more transparency on the part of China, which may be sitting on information that could more definitively confirm or deny the lab leak hypothesis. At the very least they can address the argument that they are not being transparent by being more transparent.

Going forward it seems that we need international standards of safety, transparency, and supervision for any lab dealing with viruses that can potentially cause a serious pandemic. No nation can ethically claim that they don’t have such international responsibilities, especially after the dramatic example of the COVID pandemic.

Author

  • Founder and currently Executive Editor of Science-Based Medicine Steven Novella, MD is an academic clinical neurologist at the Yale University School of Medicine. He is also the host and producer of the popular weekly science podcast, The Skeptics’ Guide to the Universe, and the author of the NeuroLogicaBlog, a daily blog that covers news and issues in neuroscience, but also general science, scientific skepticism, philosophy of science, critical thinking, and the intersection of science with the media and society. Dr. Novella also has produced two courses with The Great Courses, and published a book on critical thinking - also called The Skeptics Guide to the Universe.

Posted by Steven Novella

Founder and currently Executive Editor of Science-Based Medicine Steven Novella, MD is an academic clinical neurologist at the Yale University School of Medicine. He is also the host and producer of the popular weekly science podcast, The Skeptics’ Guide to the Universe, and the author of the NeuroLogicaBlog, a daily blog that covers news and issues in neuroscience, but also general science, scientific skepticism, philosophy of science, critical thinking, and the intersection of science with the media and society. Dr. Novella also has produced two courses with The Great Courses, and published a book on critical thinking - also called The Skeptics Guide to the Universe.