Did COVID-19 start from a “lab leak”?

Uncertainty and Misinformation

A: We don’t know for sure where SARS-CoV-2 came from, but most evidence to date supports the natural “spillover” explanation (e.g. the virus jumped from animals to humans).

There may never be a “smoking gun” for SARS-CoV-2 origins. Pandemic preparedness efforts should focus on preventing both natural and man-made spillovers of pathogens.

It’s 3+ years into the COVID-19 pandemic, and we still can’t pinpoint the moment SARS-CoV-2 first infected a human. There are two main hypotheses circulating:

The virus originated in animals and “spilled over” into humans.
The virus leaked accidentally from a lab working on coronaviruses.

Currently, the scientific community generally favors the “spillover” hypothesis rather than the “lab leak” hypothesis. This is based on various pieces of evidence, such as the genetic makeup of the virus and how it spread outward from the Huanan market in Wuhan. The first cluster of COVID-19 cases occurred in people who had visited the section of the market where live animals that are susceptible to the virus were sold. New released data on swabs of the market stall surfaces found both SARS-CoV-2 and raccoon dog DNA-an animal known to carry SARS viruses- but no human DNA. There is also a history of viruses jumping from animals to humans (“zoonotic diseases”), including in SARS-1, MERS, HIV/AIDS, Ebola, and other viruses. None of this evidence proves definitively that the market was the source of the first human cases- it’s “circumstantial,” to use the language of criminal trials.

Many people who support the theory that COVID-19 originated from a lab argue that it’s too much of a coincidence that the outbreak started in Wuhan, just a few miles away from a virology institute that collects and studies coronaviruses. However, there are no known cases of COVID-19 that can be traced back to the lab or that are geographically connected to the lab, unlike the Huanan market. Moreover, the genetic makeup of SARS-CoV-2, the virus that causes COVID-19, is not close to the strains of coronavirus being studied in the lab. This doesn’t mean that the “lab leak” theory is impossible or that it’s a “conspiracy theory,” but it does mean that it’s likelihood of being true is low. As Carl Sagan once said, “extraordinary claims require extraordinary evidence,” and so far, there is no direct evidence to support the claim that COVID-19 originated from a lab.

You may have heard about a recent US Department of Energy Report stating with “low confidence” that COVID-19 might have originated in a lab leak. The data behind this report has not been released. Overall this report highlights the lack of consensus within US government agencies. Of the eight US government agencies investigating SARS-CoV-2 origins, four lean toward it being a natural transmission but with low confidence; two haven’t made a judgment either way (including the CIA) and the other two lean toward a lab leak (but not with high confidence). So while the press coverage of the new report made it seem like something new had come out to prove the lab leak theory, that’s not really true.

Tracing the origins of a virus can take many years of careful fieldwork. Identifying with any degree of certainty that a virus originated in a certain animal and spilled over to humans requires genetic matching of virus sequences of animals and the first confirmed cases of the disease in humans. This is challenging in part because viruses can mutate quickly, so a 100% match is unlikely, but anything close to that is usually good enough to declare a match. This type of work can take years, as it did with HIV/AIDS, and like any detective work relies on a bit of luck.

Despite the fact that most scientists accept the natural “spillover” hypothesis, we must face the fact that we may never know for sure. Like a murder cold case, it’s very possible that any definitive evidence (such as live animals from the market that could be tested for SARS-CoV-2) simply no longer exists.

Regardless of whether you personally favor the “spillover” or “lab leak” theory, it’s important to keep an open mind and consider any new evidence that comes to light. This is the very essence of the scientific process. Science is not a set of fixed facts, but an ever-evolving process of testing, questioning, and updating what we know based on new information. Beware of anyone so entrenched in their beliefs that they would never change their mind regardless of new evidence. This is a good indicator that their beliefs are not based on science.

Sadly, like many things in this pandemic, the COVID-19 origins “debate” has become highly politicized. While it’s important to continue transparent and open-minded investigation of SARS-CoV-2 origins, what’s most important is preventing and preparing for future pandemics. For that goal, knowing with certainty what happened with SARS-CoV-2 doesn’t help us much.

No matter how the COVID-19 pandemic started, we need to be prepared for many kinds of threats. This means making sure governments take steps toward biosafety and seriously consider the role of high-containment labs worldwide. At the same time, we need to invest more in public health efforts to identify emerging pathogens (i.e., infectious disease surveillance systems) and reduce the chances of transmission and spillover.

In the end, we may never have an answer to the origins of the COVID-19 pandemic, and that can be frustrating and uncomfortable. But we still need to move forward and confront the potential threats that lie ahead.

Stay safe and stay well!

Those Nerdy Girls


“The Strongest Evidence Yet That an Animal Started the Pandemic”

“COVID-origins study links raccoon dogs to Wuhan market: what scientists think”

“U.S. Dept of Energy says with ‘low confidence’ that COVID may have leaked from a lab”

“How seriously should we take the US DoE’s Covid lab leak theory?”

Lab Leak Confusion blog from Paul Offit

Previous Nerdy Girl post on lab leak hypothesis

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