Genetic ghosts suggest pandemic started in market

A team of scientists has said it is “beyond reasonable doubt” that the coronavirus pandemic began with infected animals sold in a market, rather than a virus leak from a laboratory.

They were analysing hundreds of samples collected in Wuhan, China in January 2020.

The findings identify a range of animals, including raccoon dogs, civet cats and bamboo rats, as potential sources of the pandemic.

Despite pointing to one stall at the market as a hotspot for both animals and the coronavirus, the study fails to provide conclusive evidence.

The samples were collected by Chinese authorities in the early stages of COVID-19 and represent one of the most valuable scientific sources of information on the origins of the pandemic.

An initial link to the Huanan Seafood Wholesale Market was established when patients with pneumonia of unknown cause were admitted to hospitals in Wuhan.

The market was closed and teams inspected the area, including the stalls, the inside of the animals' cages and equipment used to strip fur and feathers from slaughtered animals.

Their analysis Published last year The raw data was then made available to other scientists, and now a team of researchers from the US and France has said they have carried out more sophisticated genetic analysis to look more deeply into the early stages of COVID-19.

The study analysed millions of short snippets of genetic code, including both DNA and RNA, to identify animals and viruses that were on the market in January 2020.

“We are seeing ghosts of these animals' DNA and RNA in environmental samples, and some of them [the Covid virus] “It has been discovered,” said Professor Florence Debarre of the French National Center for Scientific Research.

result, Published in Cell magazine Highlight a set of findings and synthesize those results to support your argument.

They found that the new coronavirus and susceptible animals were found in the same locations, and some swab tests picked up both animal and new coronavirus genetic code, which was not evenly distributed across the market but pointed to very specific hotspots.

“What we found was a very consistent story in that even at the level of a single food stall, markets were very likely the source of this particular pandemic,” said Professor Christian Andersen of the Scripps Research Institute in the US.

However, being in the same place at the same time is not proof that the animals were infected.

The most frequently detected animal in the samples was the raccoon dog, which has been shown in experiments to be able to become infected with and spread the new coronavirus.

Other animals identified as potential sources of a pandemic include the palm civet, the Siberian bamboo rat, and the Malayan porcupine, which were also involved in the SARS epidemic in 2003. No experiments have been done to see whether these animals can spread the virus.

Extensive genetic analysis identified a species of raccoon dog being sold that wasn't farmed for its fur but was commonly found in the wild in southern China, giving the scientists a clue as to where to look next.

The team also analysed the genetic code of the virus samples found in the market and compared it with samples from patients earlier in the pandemic. Examining different mutations in the virus samples could also provide clues.

The samples suggest, but do not prove, that the new coronavirus may have emerged multiple times at the market, jumping from animals to humans twice. The researchers say this supports the idea that the market was the source, rather than the pandemic starting somewhere else and the market adding fuel to the fire as a superspreading event.

Scientists have also used the mutations to construct a family tree of the virus, delving into its past.

“If you estimate when the pandemic probably started and when market transmission probably started, the two overlap and are the same,” Andersen says.

Their scientific paper says the full genetic diversity of the coronavirus seen early in the pandemic was found in the market.

“The market sequence isn't just one small branch on this big, bushy evolutionary tree, it's across all the branches of the tree, which is consistent with genetic diversity really starting in markets,” said Michael Worobey, a professor at the University of Arizona.

He said this study, combined with other data such as early cases and hospitalizations linked to the market, indicates that the new coronavirus originated from animals.

“There's no doubt that this happened,” Prof Worobey said, adding that any other explanation for the data required “some pretty fantastical and absurd scenarios”.

“I think there's been a lack of appreciation up until now of how strong the evidence is.”

The lab leak theory claims that the virus did not escape from a wild animal, but came from the Wuhan Institute of Virology (WIV), which has been researching coronaviruses for years.

The market is a 40-minute drive away. US intelligence agencies have been asked to examine the possibility that the leak may have been accidental or deliberate.

In June 2023, all agencies said either a leak or an animal origin were plausible scenarios.

The National Intelligence Council and four other agencies said an animal was the likely cause, while the FBI and Department of Energy considered it more likely to have been a laboratory accident.

“For a lot of people, this seems like the most likely scenario: 'The lab is right there. Of course it's a lab. Are you stupid?' I completely understand that argument,” Andersen said.

But he said there's now plenty of data that “actually shows that the market is a true early center” and “even shows locations within the market.”

Identifying the animal that may have been the source of the pandemic provides clues for scientists to search for further evidence of an animal origin.

But because the farm culled its animals early in the pandemic, there may no longer be any evidence left to find.

“Maybe we missed our chance,” Professor Worobey said.

Professor Alice Hughes of the University of Hong Kong, who was not involved in the analysis, said it was “good research”.

“[But] Without swab samples taken from animals actually caught in the market, we cannot have a higher degree of certainty.”

Professor James Wood, co-director of the Cambridge Institute of Infectious Diseases, said the study provided “very strong evidence” that the pandemic started in the market's wildlife stall, but added that it was not conclusive evidence because the samples were taken after the market had closed and the pandemic probably started several weeks earlier.

He added that “little to no measures” have been taken to restrict the live wildlife trade, warning that “uncontrolled transmission of zoonotic diseases poses a significant risk of future pandemics.”