Did a lab leak cause COVID-19? Despite the latest headlines, it’s still not very likely Trevor Sloughter The Skeptic

A glance at the headlines over the past week would imply major revelations in the study of the origins of Sars-CoV-2, the virus that causes COVID-19. In short, the Wall Street Journal reported on 26 February that the US Department of Energy has adjusted its assessment on the likelihood of a ‘lab leak’, changing its assessment of this hypothetical origin to “low confidence”, from its earlier position in 2021 that it couldn’t make a determination either way. This assessment is part of a multi-agency investigation that resulted in a now-declassified report from late 2021 and a still-classified updated report from this year.

If that paragraph sounds cautious, and if all the hedging and equivocation made it difficult to read, that’s because almost nothing has changed in the science, nor has much changed in the positions of the US intelligence community. Four of the involved agencies still lean toward a natural origin, two remain uncommitted. No new evidence has been shown to the public, and little in the press indicates what the evidence could be that would merit the headlines.

President Biden ordered eight intelligence agencies to investigate Covid’s origins shortly after he assumed office. Their approach, as can be read in the 2021 report, is one of intelligence and security. In the intervening years, independent scientists in public health, molecular biology, genetics, and other life sciences have done their own investigations, which lean far more toward a natural origin.

There are several reasons. Two interconnected studies (Worobey et al., 2022 and Pekar et al., 2022) looked at the history of the earliest cases, how they spread, and what lineages of the virus they represented. The fist paper goes into the details, and as Dr Angela Rasmussen (co-author of the Worobey paper) simplifies on Twitter, having two lineages of Covid appear in the market in the earliest days of the pandemic is hard to square with a lab-leak hypothesis. From a zoonotic origin, this makes sense: the virus was already prevalent in wild animals, inevitably in multiple lineages, and thus animals carrying those lineages could transmit to people. Were a lab leak the source, two workers would have to be exposed to two different strains, leave the lab, and travel to the same market within days of each other. Impossible? No. But is it probable, given the alternative?

This is just one line of evidence that tilts the scales toward a natural origin in the minds of so many biologists. While the lab-leak hypothesis can feel sensible given the proximity of a lab working on dangerous viruses to the early cases, it struggles to explain the clustering patterns, the spread from the market epicentre, and the two lineages all together. And good hypotheses must account for all the strands of data simultaneously, not piecewise.

The new, still-classified report may have information the public isn’t privy to, but there’s reason to be sceptical. The 2021 report states

Although the IC [intelligence community] has no indications that WIV [Wuhan Institute of Virology] research involved SARS-CoV-2 or a close progenitor virus, these analysts note that it is plausible that researchers may have unwittingly exposed themselves to the virus without sequencing it during experiments or sampling activities, possibly resulting in asymptomatic or mild infection.

This line is under the sub-heading “The Case for the Laboratory-Associated Incident Hypothesis”. To be absolutely clear, thorough investigation of a lab-leak possibility is not only warranted, but essential. It is, in fact, this kind of diligence that makes labs studying dangerous pathogens as secure as they are.

And there have been concerns for some time about the safety and security of the lab in question, as stated by the US State Department. Additionally, journalists and US Senate staffers have used to the opacity of the current government of China as reason to automatically distrust, even disregard, data that was used in studies such as Worobey et al. A joint investigation by ProPublica and Vanity Fair questions how much we can really know about the WIV without full transparency, prompting Michael Worobey to reply on Twitter taking a strong stance in defence of the reliability of the data his team used, arguing that the preponderance of available case data enabled their “unambiguous” conclusion of a zoonotic origin.

One does have to wonder how an intelligence agency can go from “no indications that WIV research involved SARS-CoV-2” to “low confidence” in a lab-leak origin of the pandemic, even with suspicion and concern about what we might not know, without a credible rebuttal to alternate analyses of epidemiological data. Identifying the possibility, and proposing a mechanism, is not in and of itself evidence, especially when evidence exists for a natural origin.

Another important note is that the US intelligence community does agree on quite a lot about Covid’s origins, as detailed in the report and summarised in Slate: they agree Covid was not a bioweapon, and that it was not tampered with through genetic engineering (eliminating the fear-mongering about ‘gain-of-function’, which is often misunderstood). This does not preclude a lab-leak origin, but it is helpful in shutting down fringe conspiracy theorists.

The lab-leak hypothesis deserves rigorous scrutiny, but the current headlines implying new revelations from the highest authorities do not constitute rigour. When it comes to the origins of Covid, the evidence for a natural origin may still rest on uncertainties and likelihoods, but the evidence for a lab leak remains little more than “not impossible”. This could yet change with new information, but the press would do well to hold their horses.

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Eye-catching headlines declare new revelations about Covid’s origin, but without more evidence, the lab-leak hypothesis remains not impossible, but still improbable
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