Genetics ghosts suggest Covid's market origins

A team of scientists says it is “beyond reasonable doubt” the Covid pandemic started with infected animals sold at a market, rather than a laboratory leak.

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

The results identify a shortlist of animals—including raccoon dogs, civets, and bamboo rats—as potential pandemic sources.

Despite highlighting one market stall as a hotspot of both animals and coronavirus, the study cannot provide definitive proof.

The samples were collected by Chinese officials in the early stages of Covid and are one of the most scientifically valuable sources of information on the origins of the pandemic.

An early link with the Huanan Seafood Wholesale Market was established when patients appeared in hospitals in Wuhan with a mystery pneumonia.

The market was closed and teams swabbed locations including stalls, the inside of animal cages and equipment used to strip fur and feathers from slaughtered animals.

Their analysis which was published last year and raw data are being made available for other scientists.

Now a team in the US and France says they have performed even more advanced genetic analyses to peer deeper into Covid’s early days.

It involved analysing millions of short fragments of genetic code—both DNA and RNA—to establish what animals and viruses were in the market in January 2020.

“We are seeing the DNA and RNA ghosts of these animals in the environmental samples, and some are in stalls where (the Covid virus) was found too,” said Prof Florence Débarre, of the French National Centre for Scientific Research.

The results, in the journal cell highlights a series of findings that come together to make their case.

It shows Coronavirus and susceptible animals were detected in the same location, with some individual swabs collecting both animal and coronavirus genetic code. This is not evenly distributed across the market and points to very specific hotspots.

“We find a very consistent story in terms of this pointing - even at the level of a single stall - to the market as being the very likely origin of this particular pandemic,” stated Prof Kristian Andersen, from the Scripps Institute in the US.

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

The animal that came up most frequently in the samples was the common raccoon dog. This has been shown to both catch and transmit Covid in experiments.

Other animals identified as a potential source of the pandemic were the masked palm civet, which was also associated with the Sars outbreak in 2003, as well as hoary bamboo rats and Malayan porcupines.

The experiments have not been done to see if they can spread the virus.

The depth of the genetic analysis was able to identify the specific types of raccoon dogs being sold.

They were those more commonly found in the wild in South China rather than those farmed for their fur. This gives scientists clues about where to look next.