Was it a few raccoon dogs, inside a metal cage and stacked on top of a chicken coop? Or maybe a solitary red fox, curled up in the corner of its cage. Could one of these wild animals have started the whole COVID-19 pandemic at the end of 2019?
Over the weekend, an international team of scientists published two detailed papers online, offering the strongest evidence yet that the COVID pandemic originated in animals at a market in Wuhan. Specifically, they conclude that the virus most likely jumped from a caged wild animal to people at the Huanan Seafood Market, where a massive COVID outbreak began in December 2019.
Scientists who weren’t involved in the research papers call the new data ‘very compelling’ and a ‘big blow’ to the lab leak theory – that the virus somehow escaped from the Wuhan Institute of Virology, which researches coronaviruses. Reacting to the articles, they say the recently released data tips the balance towards wildlife being sold on the market.
“The studies don’t entirely rule out other hypotheses,” says virologist Jeremy Kamil, who is at Louisiana State University Health Shreveport and not involved in this research. “But they are absolutely pushing it towards an animal origin.”
None of the newspapers provide irrefutable proof, that is, an animal infected with the virus in a market.
But they are getting closer. They provide photographic evidence of wild animals, which may be infected with and excrete SARS-CoV-2, sitting on the market in late 2019 – such as raccoon dogs and a red fox.
Additionally, the caged animals are shown in or near a booth where scientists have found the SARS-CoV-2 virus on a number of surfaces, including on cages, carts and machines that process animals. animals after their slaughter at the market.
The papers are preliminary. They have yet to be examined by outside scientists. But if the analyzes prove to be accurate, the new data paints an incredibly detailed picture of the early days of the pandemic. Photographic and genetic data identify a specific stand in the market where the virus was likely transmitted from animal to human. And a new genetic analysis estimates the time, within weeks, when not one but two spills occurred. He predicts the virus jumped on people once in late November or early December and then again a few weeks later.
So now, for the first time, the timing of the first known COVID infections coincides almost exactly with the timing of the outbreak in the seafood market, which began in early December and likely involved hundreds of people working or doing their market shopping. This outbreak has also spread to the surrounding community, as one of the new studies shows.
At the same time, the Chinese CDC found two different variants of the virus on the market. And an independent study, conducted by virologists at the University of California, San Diego, suggests that these two variants did not evolve in humans because throughout the pandemic scientists never detected a variant. connecting the two. Altogether, the new studies suggest that most likely both variants evolved inside animals.
Evolutionary biologist Michael Worobey helped lead two of the studies and was at the forefront of research into the origins of the pandemic. He has spent his career tracking down the origin of pandemics, including the origin of HIV and the 1918 flu.
In May, Worobey signed a letter calling for an investigation into the lab leak theory. But then, through his own investigation, he quickly found data supporting an animal origin.
This week, NPR sat down with Worobey, who is at the University of Arizona, to understand what the data from these new studies tells us about the origin of SARS-CoV-2; how, he thinks, the data can change the debate over lab leak theory; and the importance of photos taken five years before the pandemic. Here are the key points from the conversation, which have been edited for clarity and length.
Live COVID-susceptible animals were on the market in December 2019
Worobey: “It is clear that these live wild animals, including raccoon dogs and red foxes, were in the market. We have photographic evidence from December 2019. A worried customer obviously took these photos and videos from the market on December 3 and posted them on Weibo. [because it was illegal to sell certain live animals]. The photos were quickly deleted. But a CNN reporter had communicated directly with the person who took the photos. I was able to get in touch with this reporter, and they forwarded these photos from the source. So we don’t check the pictures completely.
Live susceptible animals were held in a stall where SARS-CoV-2 was later detected on a machine that processed animals in the market
Worobey: “We have analyzed a leaked report from the Chinese CDC detailing the results of this environmental sampling. Virtually all of the report’s findings were consistent with those of the World Health Organization report. But there was additional information in the leaked report. For example, there was information not only about the stalls that contained the virus – or had samples positive for SARS-CoV-2 – but also the number of samples in a given stall that tested positive.
“We discovered that one stand actually contained five positive samples – five surfaces of this stand contained viruses. And even better, in this particular stall, the samples were very animal. For example, scientists found a virus on a feather epilator/epilators; a trolley of the type seen in the photographs used to transport the cages; and best of all, a metal cage in a back room.
“So we now know that when national public health authorities shut down the market and then sampled surfaces there, one of the surfaces positive for SARS-CoV-2 was a metal cage in a back room.
“What’s even stranger – it turns out that one of the study’s co-authors, Eddie Holmes, had been taken to the Huanan market several years before the pandemic and showed raccoon dogs in one She was told, “This is the kind of place that has the ingredients needed for the interspecies transmission of dangerous pathogens.”
“So he clicks on the pictures of the raccoon dogs. In one photo, raccoon dogs are in a cage stacked on top of a cage with birds inside.
“And at the end of our detective work, we checked the GPS coordinates on his camera, and we find that he took the photo at the same booth, where five samples tested positive for SARS-CoV-2 .
“So we connected all kinds of weird data types. Together, the data tells a powerful story.
The first known cases of COVID, even not directly linked to people who were in the market, radiate from the market
Worobey: “With a virus, such as SARS-CoV0-2, which causes no symptoms or mild symptoms in most people, you have no chance of linking all the first cases to the site where the epidemic has start. Because the virus will quickly spread to people outside of where it started.
“And yet, based on clinical observations in Wuhan, about half of the first known COVID cases were people directly linked to the seafood market. And the remaining cases, which are not linked by epidemiological data, have an even closer geographic association with the market. This is what we show in our article.
“It is absurd the force of the geographical association [to the market].”
NPR: Absurd? How? ‘Or’ What? In the sense that the seafood market is so clearly at the center of this epidemic?
Worobey: “Yes. And I don’t understand how anyone couldn’t be moved, at least a little, by this data and then take this idea [of an animal origin] seriously, especially given the other things we found in these studies.
The virus jumped on people just before the outbreak in the market
Worobey: “For example, our new genetic analysis tells us that this virus had not been around for very long when the cases occurred at the market. For example, the first known patient on the market had an onset of symptoms on December 10, 2019. And we can estimate that at that time there were only about ten people infected with the virus in the world and probably less than 70 .
“So if the pandemic didn’t start at the market, one of the first five or 10 infected people in the world was at the market. And how do you explain that?
“You have to remember that Wuhan is a city of 11 million people. And Huanan Market is just one of 4 places in Wuhan that sell live animals, susceptible to SARS-CoV-2, such as raccoon dogs.
It is highly unlikely that the first outbreak of COVID would occur in the market if there were no virus source there
Worobey: “Step back and think, ‘Where is the first cluster of a new respiratory infection going to show up in this town?’ It could appear in a market. But it could also appear in a school, university or meat packing plant.
NPR: Or a biotech conference?
Worobey: “Yes. In Washington state, SARS-CoV-2 first emerged in a nursing home. In Germany, it was with an automotive supplier.
“There are thousands, maybe 10,000 other places at least as likely, or even more likely, to be where a new pathogen emerges. And yet, in Wuhan, the first cluster of cases happens to be the “one of only four places that sell live animals, out of 10,000 other places. If you’re not surprised by this, then I don’t think you understand the improbability this presents.
NPR: So how likely is this coincidence to happen – that the first cluster of cases occur at a market that sells animals that are known to be susceptible to SARS-CoV-2, but the virus didn’t actually come from the market?
Worobey: “I would put the odds at 1 in 10,000. But it’s interesting. We have an analysis where we basically show that the probability of having this case pattern [clustered , around the market]is 1 in 10 million [if the market isn’t a source of the virus]. We consider solid evidence in science.
“The analyzes we have done tell a very strong story.
“The evidence is among the best we have for any emerging virus.”
Worobey: “It is important to note that we did not find any related virus from the intermediate host. But we have plenty of other evidence.
“And the data focusing on the Huanan market, to me, is as compelling as the data that told John Snow that the water pump was poisoning the people who used it. [John Snow was a doctor in London, who helped to launch the field of outbreak investigations by figuring out the source of a cholera outbreak in the city in the mid 19th century].”
Making these discoveries brought tears.
Worobey: “Sometimes you have those rare moments where you might be the only person on Earth with access to this kind of crucial information. When I was just beginning to realize that there were more cases on the market than you would randomly expect, I felt that. And without exaggeration, this moment – these kind of moments – brings tears to your eyes.