The Lab-Leak Hypothesis is not dead

By Kent R. Kroeger (Source:; April 16, 2022)

Disclaimer: I am statistician, freelance writer and a serviceable Tex-Mex chili cook. All grammatical errors and factual inaccuracies in this essay are mine alone. And, as always, do not make financial, medical or personal decisions based on the contents herein.


The lab-leak hypothesis proposes that the SARS-CoV-2 coronavirus was leaked from the Wuhan Institute of Virology. While the theory does not necessarily require the virus to be “man-made,” that is often a key component of this theory.

The natural-origin hypothesis, in contrast, posits that the coronavirus is natural in origin (e.g., bats and/or raccoon dogs) and was spread from a host animal species to humans, most likely occurring initially through a food market in Wuhan, China.

When news broke last November that the first known COVID-19 case was, in fact, a Huanan Seafood Wholesale Market vendor in Wuhan, China and not an accountant with no clear link to the market, a couple of ‘I told you so’ emails appeared in my inbox.

When, four months later, a team of scientists released two papers offering the strongest statistical evidence yet that the epicenter of the COVID-19 pandemic was the Huanan market — thereby, presumptively, supporting the natural-origin hypothesis for SARS-CoV-2 — my inbox was flooded with personal rebukes.

“You should be ashamed of yourself for pushing the lab leak conspiracy theory,” said one email. “Congratulations Kroeger, you fell for another Trump con,” started another.

But the most hurtful admonition of them all was this one: “You chide others for letting their partisan biases infect their judgement. But face it. You’re no better.” My wife knows how to cut to the bone.

In my defense, I never claimed the lab-leak hypothesis was the definitive explanation of SARS-CoV-2’s origin. I said the lab-leak hypothesis should be seriously considered along with the natural-origin-theory and that partisan attempts to shut down legitimate inquiries into it only creates distrust and division.

And its not like interest in the lab-leak hypothesis has been limited to xenophobic Trumpers, anti-China activists, and garden-variety conspiracy theorists. In his January 2021 article — The Lab-Leak Hypothesis — New York Magazine writer Nicholson Baker was one of the first mainstream journalists to sincerely lay out the facts supporting the lab-leak hypothesis. He offered no smoking gun, just a compelling litany of circumstantial evidence that cut through the partisan hackery attempting to the drown the lab-leak hypothesis in its infancy.

By the time Jon Stewart appeared on The Late Show with Stephen Colbert in June 2021 mocking those still clinging to the belief that SARS-CoV-2 was a natural creation, the lab-leak hypothesis had gone fully mainstream — perhaps the dominant view.

But the natural-origin hypothesis has made a comeback, and for good reason. While not definitive, significant evidence still supports the animal-to-human scenario.

What we know with some certainty about the early pandemic

U.S. Intelligence Community assessments concluded that Chinese officials became aware of SARS-CoV-2 in November 2019 and, according to Dr. George Gao of the Chinese Center for Disease Control and Prevention, Chinese officials collected extensive environmental samples from the Huanan Seafood Market in January 2020, including from 18 animal species present at the market.

From all outward appearances, Chinese officials made the Huanan market the prime suspect from the beginning.

Along with the recently released geospatial statistical analysis that found the earliest Wuhan cases of COVID-19 clustered around the Huanan market, analytic efforts have resulted in three generally accepted findings:

(1) The first known human infection of SARS-CoV-2 was a vendor at the Huanan market and the subsequent spread of COVID-19 clustered around the that market.

(2) The two original mutations of the SARS-CoV-2 virus — lineage A (which is related to similar bat coronaviruses, though its discovery in humans has been less frequent than lineage B) and lineage B (which was the first to infect humans and has been more common in humans) — were present in the Huanan Seafood Market in early January 2020. Finding these two mutations in the same geographic location supports the theory that the jump to humans occurred at the Huanan market.

(3) While there were animals at the Huanan market capable of carrying and spreading SARS-CoV-2, among those tested in January 2020, none were found to have the SARS-CoV-2 virus. However, according to Gao, Chinese officials did not test every species available at the Huanan market, including raccoon dogs which are capable of spreading the virus to humans. Is there any wonder why conspiracies theories form when such inexplicable government decisions occur?

Was it not in the Chinese government’s interest to identify the animal origin-species for SARS-CoV-2 as fast as possible? Nothing would have killed the lab-leak hypothesis faster.

And it is not like Chinese scientists are inexperienced in the virology forensics required to identify a virus’ animal origins. They identified the probable animal source of the 2003 SARS-CoV virus within months of its spread to humans.

And, most discouraging, it may be too late to find the original animal-carrier(s) of SARS-CoV-2 and, thereby, definitively confirm the natural-origin-hypothesis.

“The clincher would be direct evidence that some mammals at the market were infected with the SARS-CoV-2 virus,” wrote Michael Le Page for the The New Scientist about the virus’ possible origins. “But that almost certainly doesn’t exist any more.”

As of now, no such direct evidence exists and perhaps never will — which is a nagging problem for proponents of the natural-origin hypothesis, whether they are willing to acknowledge it or not.

Why the lab-leak-theory will survive…for now

The fact remains, prior to the COVID-19 pandemic, no virus in nature was found to have the same (or nearly the same) genetic structure as SARS-CoV-2. The closest known match (RaTG13), found in bats in southern China, is considered by virologists, including a nationally-known virologist I consulted with before writing this essay, as too genetically different from SARS-CoV-2 for any man-made genetic modification techniques (e.g., gain-of-function research) to bridge the gap.

But there are still too many questions to close the book on the lab-leak hypothesis.

SARS-CoV-2 has no known direct antecedent in nature, and lacking concrete evidence otherwise, the lab-leak hypothesis has an oxygen supply.

Lab-leak hypothesis supporters are probably not persuaded by the geospatial studies showing the earliest COVID-19 sufferers clustered around the Huanan market. Their sample of those individuals were drawn from Chinese/WHO records and Weibo, China’s most popular social media platform — but how can we be certain they are representative of the early SARS-Cov-2 infected population in Wuhan? It is not clear from these recent geospatial studies how the investigators tested for sample biases or corrected for it if it existed.

If early assumptions about the source of the SARS-CoV-2 virus centered on the Huanan market, it is not surprising that Chinese government, WHO and social media reports may have concentrated on finding infected patients in its vicinity. It is potentially a serious selection bias problem.

Furthermore, who is to say a virus housed in the Wuhan Institute of Virology — natural or man-made — didn’t leak into Wuhan’s natural environment and subsequently emerge in its local food supply (i.e., the Huanan market)? Would that scenario play out differently in geospatial analyses?

The Huanan market resided in one of the most densely populated sectors in Wuhan. How many WIV employee lived near the Huanan market or frequented its vendors?

The latest research on SARS-CoV-2 origins is persuasive but raises as many questions as it answers, and while it has shifted my confidence between the two competing hypotheses (I now lean slightly towards the natural-origin hypothesis), it hardly closes the book on the debate.

The lab-leak hypothesis remains alive.

  • K.R.K.

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