We have come to the "best" evidence so far that the virus that causes covid-19 has been transmitted to humans for the first time, claims a team of scientists.
It is the latest scientific twist in the troubled, highly politicized search for the cause of the worst pandemic in a hundred years, which has produced several competing theories that have neither been conclusively proven nor disputed.
The latest analysis points to a specific species as the most likely animal origin of the virus.
That analysis is based on evidence collected three years ago from the Huanan Wildlife Market in Wuhan, China, which was at the heart of the initial outbreak.
During the early days of 2020, when covid was still a mysterious disease, China's Center for Disease Control (CDC) took samples from the market.
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The genetic information contained in those samples only recently, briefly, became available to the public, which allowed a team of researchers to decode them and point to raccoon dogs as possible "intermediate hosts" from which the disease was transmitted to humans.
The bottom line of this analysis is that the DNA of raccoon dogs, wild mammals that are sold alive in the market as meat, was found in the same locations in the market where swabs positive for SARS CoV-2 were taken, according to the analysis published online on March 20.
But in the chaotic search for the origin of the infection, during which the market was closed a long time ago and all the animals that were sold were killed, we still have no definitive proof.
The three-year delay in publishing this key data has been described by some scientists as "scandalous".
The findings were published amid indications that the theory of the virus escaping from the laboratory is gaining momentum among US authorities.
The Chinese government has vigorously rejected suggestions that the virus originated in a scientific institution, but The FBI now believes that scenario is "most likely.", just like the US Department of Energy.
Various US departments and agencies have investigated the mystery in the past and produced different conclusions, but on March 1 the director of the US Federal Bureau of Investigation (FBI) accused Beijing of "doing everything to thwart and cover up" the investigation and disclosed that the FBI "for some time now" believes in the theory about the "escape" of the virus from the laboratory.
The BBC spoke to some of the scientists who participated in the three-year mission to investigate the origins of covid.
They believe that this new analysis is the closest we will come to understanding where the infection originated and that divisions between China and the West are hindering this scientific effort to solve the mystery.
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What does this new research show?
The complete genetic sequences from these key swabs from the market were first discovered by Dr. Florence Debar, a senior researcher at the Institute of Ecological and Environmental Sciences in Paris.
It is for a BBC World Service show "Science in Action" stated that she had been "obsessed" with finding the data since she first learned it existed.
Finding and downloading the codes from GISAID's genetic database, where scientists share similar information with each other, she and her colleagues decided to find out which animal species matched the samples found in the same location as the virus.
"We saw the results come up on our screens and they all read: raccoon dogs, raccoon dogs, raccoon dogs," she recalls.
"And so we found those animals and the virus in the same place.
"It does not prove that these animals were infected, but it is a very convincing interpretation of what we found," Dr. Debar explained.
According to Professor Eddie Holmes from the University of Sydney, who also took part in the study, this is "the best evidence for an animal origin of the virus that we will get".
"We'll never find that intermediate animal host - it's just gone."
"But it's remarkable that the genetic data has revealed these ghosts - and it absolutely shows us not just what species were present, but exactly where they were in the market," Professor Holmes told the BBC.
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What can scientists do now to discover the origin of covid?
This new data may provide more clues for future investigations into the source of the outbreak, but following up those clues will be very complicated.
Professor Marion Koopmans from the Erasmus University in Rotterdam was part of the investigation team of the World Health Organization that traveled to Wuhan in 2020.
She explained that the new analysis "located their presence at specific stalls, so you can find out where the animals that were sold there came from".
"Of course, if it was part of an illegal sale, the question is whether we will ever find out," he adds.
There could still be biological evidence on the farms where these animals were raised for sale.
If researchers could find cultured animals with antibodies showing they had been infected with SARS-CoV-2, that could provide another clue.
This genetic information could at least narrow down the search area.
But finding the specific virus in an animal, says Professor Holmes, will be very difficult.
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Does this answer the question of how the pandemic started?
This is not definitive proof.
We may never have him.
The search for that proof has itself become highly politicized and often toxic.
And while this lends some weight to the theory that the virus emerged in wild animals and passed to humans in the market, another theory focused on the possibility of a "lab escape" of the virus from the Wuhan Institute of Virology.
That theory recently resurfaced in the world news after the FBI's intervention, weeks after an intelligence assessment by the US Department of Energy and hearings initiated by Republicans on the origins of the pandemic.
In an interview with the BBC program "Science in Action", Professor Holmes pointed out a previous study of the earliest known cases of covid in Wuhan.
"The infection first appeared around the market, and now we see why - the key animals were there.
"It did not break out around the laboratory, which is 30 kilometers away. There is no data indicating early cases of infection around the laboratory," he says.
The years-long delay in releasing this precious data has led to frustration and anger at China's Centers for Disease Control (CDC).
"The data is three years old - it's an absolute scandal that it took so long to come to light," the professor points out.
The information was actually published in GISAID's genetic database back in February 2022.
But they remained there unnoticed.
It is assumed that this was done to present additional evidence for the study based on data collected by Chinese researchers from the CDC.
(The sharing of such material is considered a request for publication in scientific journals.)
But soon after Chinese researchers learned that others had seen the information, it became hidden again.
At a press conference on March 17, Tedros Adhanom Ghebreyesus, director-general of the World Health Organization, said that "any piece of information" that brings us closer to an answer is important.
"And any information related to the study of the origin of covid-19 must be shared with the international community immediately."
"We need to get beyond politics and get back to pure science," says Professor Holmes.
He also adds that "humans get infected with viruses from wild animals, which happens throughout evolutionary history".
"The best thing we can do is to separate ourselves from the wildlife world and have better control over what's going on."
"Because this will happen again," he adds.
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