Where did COVID-19 originate? The Saskatoon lab is helping with genetic analyzes that point to the animal market

A team of scientists, including one in Saskatoon, say they have strong evidence that the COVID-19 virus passed from infected animals to humans, rather than originating from a laboratory leak.

The analysis of hundreds of genetic samples provides strong but indirect evidence that the origins of the pandemic are linked to the wildlife trade at the Huanan Seafood Wholesale Market, said Angie Rasmussen, co-author of the study and virologist at the Vaccine and Infection Disease Organization of the University of Saskatchewan. .

The study, published this fall in the journal CellResearch shows that the virus emerged in the market in Wuhan, China, at the same time the pandemic began in the human population, suggesting it was its place of origin and linked to the live animals sold there.

“It's very difficult to explain it in any other way, except that the virus was brought there with those live animals and spread, twice in fact., in the human population on the market,” she said.

There were two main theories about the origins of the COVID-19 pandemic, which were declared by the World Health Organization in March 2020. The first was that the virus passed from an infected animal to a human, most likely in the market; the second was that the virus had leaked from the Wuhan Institute of Virology.

Even as the pandemic raged, pinpointing its origins quickly became a high priority for the world's top scientists.

While other studies looked at the presence of the virus in the market, this analysis looked at the genetic samples present there at a snapshot in time. This included samples from some animals that are known hosts and vectors of coronaviruses, such as raccoon dogs, bamboo rats and palm civets.

LOOK | The Saskatchewan lab is investigating the links between COVID-19 and animals:

New evidence for COVID-19 came from animals – not from a laboratory in Wuhan

A team from Canada's Center for Pandemic Research says they have found strong but indirect genetic evidence that COVID-19 jumped from animals to humans in Wuhan, China. Despite mounting evidence of animal origins, many still believe it was leaked from a Chinese virology lab.

There is a good chance of a link with animals, says research

The researchers were able to determine exactly which species were present in hotspots where the virus was spreading.

The analysis does not prove that the animals in those areas were infected. However, the proximity of the COVID-19 samples to where their DNA was located means they are highly likely to be carriers, according to the study.

Dr. Lisa Barrett, an infectious disease specialist at Dalhousie University in Halifax, said the study is a good example of “very careful and fairly unbiased science” that could help prepare for future pandemic responses. It shows the importance of considering animal density in relation to people and monitoring wildlife trade, she said.

“If we don't understand exactly how viruses spread and under what conditions they spread, we will always underestimate, or not estimate at all, where the next threat will come from,” she said.

“If you don't know the why, history tends to repeat itself in the worst ways.”

Reading genetic clues

Rasmussen has been working with an international research team of top virologists since 2020, examining publicly available evidence to investigate the origins of the pandemic. Another Canadian scientist, evolutionary biologist and professor at the University of Arizona, Michael Worobey, is also on the team.

The team's previous research, along with other peer-reviewed studies, had found that the Huanan Market was the most likely place for the pandemic to spread to humans, especially related to the live animal trade.

Then in March 2023, a large dataset quietly became available online on a site where scientists share genetic sequences for research. The same data was used by Chinese scientists to publish a study in the journal Nature in 2023.

The research team soon began analyzing the genetic clues collected from swabs of surfaces in the market.

The scientists say the new evidence makes the lab leak hypothesis incredibly difficult to support.

All the data analyzed in the recent study – the early cases and proximity to market, the location of animals and the two independent spillovers to the human population, which occurred weeks apart in late 2019 – indicate that COVID-19 has its origins finds on the market. .

“None of this can be explained by a lab leak,” Rasmussen said.

For that to happen, Rasmussen said someone would have had to get infected in the laboratory at the Wuhan Institute of Virology and then go to the market without infecting anyone else. Exactly the same thing should happen again with the second line of the virus.

“When we talk about preventing future pandemics, we need to focus our resources on the problem that is much more likely to occur, rather than the hypothetical problem that is completely unsupported – and that would be the laboratory leak theory,” Rasmussen said.

Why the lab leak theory spread

The theory that the COVID-19 pandemic began after a laboratory leak began circulating in the early days of the pandemic. As more data gradually became available, top virologists – including Rasmussen's team – argued that the evidence strongly pointed to the possibility of animal transmission.

Timothy Caulfield, a professor at the University of Alberta and an expert on health and science misinformation, said many people promoting the idea of ​​a leak are trying to create broader distrust in scientific institutions.

“If you don't believe the lab leak theory, you're the enemy,” he said. “It is really considered a truth that it has been conclusively determined that the lab leak is the source and if you think otherwise you are simply wrong.”

Rasmussen and her colleagues have become the target of online attacks because of their work.

“We are accused of running a propaganda campaign designed primarily to cover up the real story of a laboratory leak. But that's just not true,” she said.

Caulfield said the idea of ​​a lab leak continues to spread widely, embraced by politicians in the U.S. and Canada and by people who feel compelled to support the beliefs of their political groups.

“The idea that this was a deliberate action by a malevolent force, I think, is also part of and closely tied to the lab leak theory, and one of the reasons we still hear about this today,” he said.