New evidence that Covid-19 spilled over from animals

During the past three years, the origins of the Covid-19 pandemic have been intensely debated. While some scientists argued that the virus initially emerged in wild animals traded at the Huanan market in Wuhan and then spilled over to humans, others claimed that the virus may have leaked from the Wuhan Institute of Virology.

Although it is likely that the origins of the pandemic will remain a mystery, new genetic evidence that emerged this week points to the possibility that racoon dogs – small, heavy-set, fox-like canids native to East Asia – might have started the pandemic.

Initially, swabs collected from stalls at the Huanan market in the first months of 2020 were found to contain only SARS-CoV-2 and human DNA. However, at the beginning of this week Florence Débarre, an evolutionary biologist at the French National Center for Scientific Research (CNRS), discovered a series of genetic sequences in several coronavirus-positive samples posted on the virology database GISAID that contained significant amounts of DNA from racoon dogs, as well as traces of animal DNA from civets and other mammals known to be highly susceptible to SARS-CoV-2.

Following her discovery, Débarre shared the data with an international team of world-famous scientists currently investigating the origins of the pandemic, as well as with the World Health Organization. 

“We were able to figure out relatively quickly that at least in one of these samples, there was a lot of raccoon dog nucleic acid, along with virus nucleic acid,” said Stephen Goldstein, a virologist at the University of Utah. Nevertheless, he stressed that the jumbling together of genetic materials from the virus and the animal does not conclusively prove that a racoon dog was initially infected and then passed the virus to humans; in fact, it is possible that the opposite scenario might have happened, with various animals catching the virus from humans.

However, according to Michael Worobey, an evolutionary biologist at the University of Arizona, this finding is “just one more brick on this massive wall of evidence that all fits together. If it weren’t so politicized, it’s one of the clearest sets of evidence for how a pandemic emerged that we’ve ever had.”

“Top line is that there were animals at the market and they are in the exact location where the virus was,” added Angela Rasmussen, a virologist at the University of Saskatchewan. “We can’t say for sure that they were infected, but this is very strong evidence supporting that the pandemic’s origin was due to the live animals at Huanan market.”

After analyzing the genetic sequences, the experts reached out to the Chinese scientists that originally posted the data on GISAID for a possible collaboration but, soon after that, the data disappeared from the database, highlighting once more the intensely politicized dimensions of the pandemic, and China’s refusal to admit the massive illegal wildlife trade occurring in its markets. 

This led WHO director-general Tedros Adhanom Ghebreyesus to renew his call for China to share scientific data on the origin of the pandemic on Friday. “We continue to call on China to be transparent in sharing data, and to conduct the necessary investigations and share the results. Understanding how the pandemic began remains both a moral and scientific imperative.” 

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By Andrei Ionescu, Earth.com Staff Writer

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