Evidence points to Wuhan market as source of covid-19 outbreak

Analysis of genetic samples collected from the Huanan Seafood Market in Wuhan, China, found that some of the wild animals sold there were the most likely source of the virus that sparked the coronavirus pandemic.

While bats are thought to be the original carriers of the SARS-CoV-2 virus, it has previously been suggested that an intermediary wild species became infected and brought it to the market, where stalls sold live animals and seafood, sparking the human outbreak.

Another theory is that the virus leaked from the Wuhan Institute of Virology, where staff are known to be studying bat coronaviruses, but not SARS-CoV-2.

However, new research by an international team concludes that the virus is more likely to have come from wild animals sold at the market rather than escaped from a laboratory. The researchers reanalyzed data from 800 samples collected by the Chinese Center for Disease Control and Prevention at the Huanan Seafood Market starting on January 1, 2020, and studied viral genomes from the earliest cases of covid-19.

Team Members Ed Holmes The University of Sydney researchers said Chinese investigators swabbed surfaces, freezers, drains and cages to test for the presence of SARS-CoV-2.

“We analyzed this data to determine which species were present in the market and where they were found, specifically in relation to where SARS-CoV-2 had been found,” Holmes said.

Contrary to some claims by Chinese investigators, the team found evidence that a variety of wild animals sold at the market could have been intermediate hosts for the virus, including raccoon dogs (Raccoon）、civet cat（Civet) and Gray Bamboo Rat (Pink-spotted bamboo rat).

Importantly, traces of the animals were found in the exact same corrals as traces of SARS-CoV-2, Holmes said. “This suggests — but does not prove — that the animals were infected. Therefore, it is likely that SARS-CoV-2 was present in the live animal markets.”

“All scientific data points in one direction — the natural zoonotic origin of SARS-CoV-2 was in the Wuhan Huanan Seafood Market,” Holmes said.

Genetic studies of the virus from the earliest COVID-19 cases suggest that few people were infected before the outbreak at the market, the team reported. However, it cannot be ruled out that the virus was brought into the market by infected people who came into contact with animals.

Team Members Zach Hensel Researchers at the Universidad Nova de Lisbon in Portugal said the study highlighted the preventable risks posed by human-wildlife contact at the Huanan Seafood Market and the need to mitigate these risks at similar locations.

“Although the Huanan seafood market was full of people and live mammals were concentrated in a few stalls, human viruses other than SARS2 were rare, while several animal viruses were quite abundant,” Hensel said.

“These include an influenza virus with zoonotic spillover potential and an animal virus that is closely related to other viruses that have caused significant outbreaks in animals.”

Hensel said that using simple personal protective equipment in such settings would have been recommended before the COVID-19 outbreak and could have prevented the entire outbreak.

Robert Edwards Researchers at Flinders University in Adelaide, Australia, who were not involved in the study, said a “dream team of evolutionary biologists” conducted the latest research.

“There is now no doubt that the origin of SARS-CoV-2 was from seafood markets,” Edwards said. “The authors discuss human infection at seafood markets, but any other origin story would have to explain why seafood markets were the source of so many outbreaks.”