Has the lab leak theory really been disproved?

The BBC carried a story this week with the headline ‘Covid origin studies say evidence points to Wuhan market’. Bizarrely the paper in Science they are referring to, by Michael Worobey and colleagues, says no such thing. It says: ‘the observation that the preponderance of early cases were linked to the Huanan market does not establish that the pandemic originated there’.

All three of the scientists quoted in the BBC story have been highly dismissive about even discussing the possibility that the pandemic began as an accident in a Wuhan laboratory. Their vested interest is clear: they worry that the reputation of their field of virology would be threatened by such a discussion. But the many scientists who say such a debate is needed are largely ignored by the BBC: none are quoted in this week’s article.

The Beeb’s story says that ‘this evidence paints a picture that Sars-CoV-2 was present in live mammals that were sold at Huanan market in late 2019’. This too is wrong. Nobody has found any evidence of Sars-CoV-2 in live mammals at the market. They have found some evidence – they cite only a YouTube video – that mammals were on sale in the market, which we already knew, but not that the mammals were infected. That would be the very minimum requirement for asserting that the pandemic began in the market. In 2003 scientists refused to assert that Sars began in markets till they found infected animals.

The new paper shows that lots of early cases had visited the Huanan seafood market or lived near it, which we already knew. But for the first two weeks of January 2020, the Chinese authorities were defining pneumonia cases as (what we now call) Covid only if they had visited or lived near the market: so it is a circular argument. The scientists dismiss this ‘ascertainment bias’ problem by citing one of their own papers, which simply asserted that this problem could be ignored. As Dr Alina Chan of MIT and Harvard puts it: ‘Worobey et al. are claiming that there is no ascertainment bias because their lead author said so.’

The new Science paper has an ignominious history. It began life as a ‘preprint’ whose data and logic were torn apart within days by independent researchers. Even the Chinese Academy of Sciences panned it for ‘obfuscating the epidemic outbreak place…and the origin’ and for ‘overstating conclusions based on limited data and unrealistic simulations’. Senior Chinese scientists published a preprint the same week reiterating their conclusion that the market was a place where the early outbreak was amplified, not where it began. It’s quite something when western scientists go further than those supervised by the Chinese Communist party in trying to exonerate a possible lab leak. Yet its conclusions were reported by the Times as having ‘found patient zero’ and the New York Times as saying 'the virus was present in animals’ at the market – both entirely false claims.

As published, the paper is now a damp squib. Gone is all the certainty of the preprint. Where the preprint claimed ‘dispositive evidence for the emergence of Sars-CoV-2’, the paper now cites ‘insufficient evidence to define upstream events’. Where the preprint said the market was the ‘unambiguous epicentre’ of the pandemic, the published paper now admits that ‘exact circumstances remain obscure’.

There is one very misleading sentence: ‘This region of Hubei contains extensive cave complexes housing Rhinolophus bats, which carry SARS-CoVs’. The bat colonies near Wuhan have been extensively sampled, very few SARS-like viruses were found, and none at all like SARS-CoV-2. Most serious scientists agree that this virus probably came from bats on the borders of Yunnan and Laos. The question is and always has been: how did the virus get to Wuhan from bats living more than a thousand miles to the south-west, a distance as great as London to Rome?

One possibility is the wildlife trade, but far less wildlife is sold in Wuhan than in Guangdong in southern China, and yet the virus appeared only in Wuhan: where are the other outbreaks among wildlife traders. The other possibility is that it was scientists who brought it to Wuhan. Why do we think this still needs discussing? Here are six good reasons.

1. Wuhan is the site of the most intensive programme of research on SARS-like viruses in the world

2. That programme involved bringing hundreds of SARS-like viruses to Wuhan

3. Most of them were brought by scientists from Yunnan and some from Laos

4. Among those viruses was one that was 96.2 per cent the same as SARS-CoV-2

5. They refuse to open up their database showing what other viruses they brought and they published the results of experiments in which they manipulated the genomes of these viruses in ways that sometimes made them much more infectious

6. They published plans to insert into a SARS-like virus the very kind of genomic sequence that SARS-CoV-2 has and no other SARS-like virus has.

None of this is a smoking gun, but it’s a heck of a coincidence.