Don’t believe the Chinese wet market theory for Covid
No, there is no new evidence that Covid originated with a raccoon dog in a market in Wuhan. The public relations blitz that surrounded the publication this week of a paper in Cell from a team whose previous papers have been debunked caught some headlines, as it was designed to do. The market theory is still implausible, as George Gao, the man who led the investigation of that market, Ralph Baric, the world’s leading coronavirologist, and many others insist.
The new study says there were mammals on sale in the market. We knew that: it was in our book published three years ago. It says there was SARS-CoV-2 in the market; yup, in our book. It says there were two strains in the market, A and B. Well, every human infection in the market was the B strain; the only sign of the older A strain was on a single glove, possibly contaminated in a lab. It says both animals and viruses were concentrated in the south-west corner of the market. Yes, that’s because, the Chinese scientists say, they focused their search on the stalls that had been selling mammals!
None of this is new. What the new paper does not say, because it cannot, is that there was an infected mammal in the market; or a market vendor infected by a mammal. These are the bare minimum clues that in every other zoonotic outbreak scientists have demanded to see. Other viruses that do infect raccoon dogs are in close association with raccoon dog DNA in that market, whereas SARS-CoV-2 is less associated with raccoon dogs in the market samples even than fish.
The new paper’s reasoning demands that a single infected raccoon dog somehow souped up a bat virus enough to spark a global human pandemic without sparking even a single other case among, er, raccoon dogs – and then vanished into thin air.
Bizarrely, the one new piece of data in the new paper points away from the market: the geographic origin of the mammals. The raccoon dogs came from central China, near Wuhan, where close relatives of the pandemic virus have never been found.
Shockingly, but not surprisingly, the paper also shows evidence of biased reasoning. In trying to pin down the date of the most recent common ancestor of the human infections, it uses an inappropriate statistical technique which conveniently excludes most early cases, inferring a late November-December date that coincides with the likely market outbreak. All the other good studies have concluded that the first infection occurred much earlier.
There are thousands of markets selling raccoon dogs all over China and south-east Asia. Yet by spectacular bad luck, the virus turned up only in the one city in the whole of Asia that has a laboratory focused on collecting, studying, growing and genetically manipulating SARS-like viruses and infecting humanised mice with them: Wuhan.
The lab was doing risky experiments that made bat viruses more infectious in the years leading up to the pandemic. It had a reputation for being unsafe. It was planning to switch its focus to viruses precisely like this one the year before the pandemic. It worked on a close relative of SARS-CoV-2 in 2018. It was party to a plan to insert a special feature into a virus’s spike gene, a feature found uniquely in the virus that caused the pandemic.
To the delight of the Chinese government, western virologists are keen to deflect the blame, even when they cannot point to an infected mammal in the market. Yet even the Chinese authorities have concluded that that raccoon dog won’t hunt.
Matt Ridley is the co-author with Alina Chan of ‘Viral: the search for the origin of Covid-19’