What is a raccoon dog and did it really cause the COVID pandemic? Here's what scientists say

A new thread in the debate over SARS-CoV-2’s origins centers around a dog-like creature from Asia

By Troy Farah

Science & Health Editor

Published March 21, 2023 12:00PM (EDT)

Raccoon Dog (Nyctereutes procyonoides) (Getty Images/Martin Moxter)
Raccoon Dog (Nyctereutes procyonoides) (Getty Images/Martin Moxter)

A cute, dog-like animal has emerged as the chief culprit for the first transmission of the COVID virus to humans, thanks to newly revealed genetic evidence from the Huanan Seafood Wholesale Market in Wuhan, China. Based on these new facts, common raccoon dogs, a species that resembles a fox-raccoon hybrid, may be the "patient zero" that triggered the global public health disaster we're still suffering through.

An exclusive report from Katherine Wu at The Atlantic presents the strongest evidence to date that SARS-CoV-2, the virus behind the brutal pandemic now entering its fourth year, first appeared in animals before jumping to humans. The genetic evidence pushes back against the narrative that the pathogen was accidentally or intentionally leaked from the Wuhan Institute of Virology.

The debate on COVID's origins have divided people across the scientific and political spectrum, but direct evidence has been hard to come by. Yet this latest bit of evidence may be the best data we ever get.

A new analysis of swabs taken from market stalls in and around the pandemic's alleged ground zero in January 2020 found a mix of SARS-CoV-2 genetic material, but also included that of common raccoon dogs (Nyctereutes procyonoides). These are small, wild canids (a family of mammals including foxes, wolves and dogs) found in East Asia, including China and have long been known to harbor coronaviruses.

In fact, a study published last February in the journal Cell, which identified 65 previously undescribed virus species in Chinese game animals, reported that some raccoon dogs harbored coronaviruses with 85 to 94 percent similarity to human coronaviruses detected in Haiti and Malaysia. Coronaviruses are a broad category of viruses that all have similar shape: a ball with spikes resembling a crown.

It wasn't initially clear that raccoon dogs were even at the market in Wuhan until later evidence emerged in 2020 revealing the animals were illegally kept at the marketplace. 

While most coronaviruses either have no effect or cause simple colds, some like MERS, SARS and SARS-CoV-2 can be deadly. We know that many mammals naturally have these pathogens and they occasionally spill over into humans, especially as we destroy more of their environment, not to mention poach and eat wild animals. If an animal infected with a coronavirus comes in close contact with humans as result, most coronaviruses have no qualms about moving to a new, human host. 

Raccoon dogs were implicated in the first SARS-CoV-1 (known at the time simply as SARS) outbreak approximately two decades ago, as wild raccoon dogs have been found to naturally carry it. Although this is pretty clear evidence, virologists still aren't 100 percent sure that they caused that pandemic, which peaked in 2003. It's not easy to definitively prove an animal allowed a virus to jump to people. We still don't know where Ebola first came from, though bats are generally assumed to be the origin.

It wasn't initially clear that raccoon dogs were even at the wet market in Wuhan until later evidence emerged in 2020 revealing the animals were illegally kept at the marketplace. Again, this isn't 100 percent proof that raccoon dogs started the pandemic, but the pairing of these two genetic signatures together is pretty strong evidence, possibly the strongest we'll ever get.

According to Wu, the new analysis provides "clear-cut evidence that raccoon dogs and the virus were in the exact same spot at the market, close enough that the creatures might have been infected and, possibly, infectious."

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To reach this conclusion, Florence Débarre, an evolutionary biologist at the French National Centre for Scientific Research, was trawling an open-access genomic database called GISAID (Global Initiative on Sharing Avian Influenza Data) when she noticed several sequences. They'd been quietly posted by researchers from China's Center for Disease Control and Prevention several weeks ago.

When Débarre downloaded the data around March 9, forwarded it to colleagues and analyzed it, they found traces of SARS-CoV-2, as expected. That was already known by the same group of Chinese researchers who uploaded it in the first place. Last year, they published a preprint analyzing the data, (but not the data itself) stating this was "convincing evidence" that SARS-CoV-2 was present at the market during the early stages of the COVID outbreak. But they also claimed "no animal host of SARS-CoV-2 can be deduced."

This new analysis isn't likely to sway any of the hardcore believers that a lab leak alone explains SARS-CoV-2's origins. But to date, there is still no hard evidence of that being the source.

By taking a closer look, several prominent researchers who have been tracing SARS-CoV-2's origins noticed plenty of evidence contradicting that claim. On March 20, they posted a full report online, which they claim underscores the "large body of evidence supporting a natural origin of SARS-CoV-2." There was plenty of animal DNA, and a lot of it belonged to common raccoon dogs. When they contacted the Chinese researchers, the data was mysteriously deleted from GISAID. At this point, it's not clear why this data was posted, let alone removed, though Science noted it was at the "request of the submitter."

George Gao, the former China CDC director-general, also told Science and Reuters this data was "nothing new." However, this new evidence is clearly making waves. The World Health Organization director-general Tedros Adhanom Ghebreyesus said on Friday, March 17, "These data could have — and should have — been shared three years ago," but he also noted "these data do not provide a definitive answer to the question of how the pandemic began."

This new analysis isn't likely to sway any of the hardcore believers that a lab leak alone explains SARS-CoV-2's origins. But to date, there is still no hard evidence of that being the source. Even the handful of U.S. intelligence agencies (and not the majority) that claim a lab leak is plausible make their assertions with "low confidence" and zero hard evidence.

Arguments on both sides of this issue have persisted since the outbreak first happened, and scientists will likely be arguing about this for many years to come. What this new analysis could actually help with is encouraging more transparent sharing of data and galvanize researchers to study wild raccoon dogs, bats and other potential animal hosts that could lead to the next pandemic.

By Troy Farah

Troy Farah is Salon's science and health editor specializing in drug policy and pandemics.

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