An expert group of investigators convened by the World Health Organization and China to examine the murky, complex origins of the coronavirus pandemic have revealed initial conclusions from a fact-finding mission that began just under two weeks ago. Liang Wannian, one of the scientists with China's National Health Commission, told reporters in a press conference Tuesday that the team hasn't found clear evidence of an animal-to-human spillover.
"We came here with two goals," said Peter Ben Embarek, a WHO expert in food safety and zoonosis (disease that's transmitted from animals to humans), "One was to try and get a better understanding of what happened at the beginning of the event in December 2019. In parallel, we also embarked on trying to understand ... how did the virus emerge."
Two hypotheses have arisen since the beginning of the pandemic. A majority of scientists believe SARS-CoV-2, the virus that causes COVID-19, originated in bats and made a jump into humans, potentially through an intermediate species. Another theory, gaining momentum in recent months, is the notion that a bat coronavirus may have been brought back to a Wuhan lab and then accidentally escaped.
The WHO's team of 14 scientists and researchers exited hotel quarantine in Wuhan on Jan. 28 and spent 12 days visiting sites in Wuhan, including the Huanan Seafood Market, where many of the early cases were found, and the Wuhan Institute of Virology, which was known to be researching bat coronaviruses and has been hypothesized as a site of an accidental laboratory leak.
Liang, team leader Ben Embarek and Marion Koopmans, a virologist at the Erasmus University Medical Center in the Netherlands, presented findings and took questions from journalists. They evaluated four hypotheses: a direct jump from animal to human, an introduction to humans via an intermediate host, the virus arriving in Wuhan via frozen food products and a lab-related incident.
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The conference was light on data, but of the four hypotheses, the team concluded that a lab origin is "extremely unlikely." A jump from a bat via an intermediate species is said to be the most likely.
"To me, the most important conclusion is that the virus is of natural origin," said Roger Frutos, a molecular microbiologist at the French Agricultural Research Centre for International Development, or CIRAD, not affiliated with the investigation. "It closes the door to the accident or engineering theories."
Other findings, as revealed by the panel:
On the earliest cases and the Huanan Seafood Market
- "The findings indicated that there is no substantial unrecognized circulation of SARS-CoV-2 in Wuhan during the latter part of 2019," said Liang.
- It's not possible to determine how SARS-CoV-2 was first introduced to the Huanan market.
- "The onset date of the earliest case in this research was Dec. 8," said Liang. This conflicts with data published in journal The Lancet, which suggests the first case is from Dec. 1.
- Liang also suggested circulation in regions outside of China may have occurred prior to December 2019, when the virus was first detected in Wuhan. This theory and the publications surrounding it are considered flawed. "We did not find evidence of large outbreaks that could be related to COVID-19 prior to Dec. 19 in Wuhan or elsewhere," Ben Embarek noted.
- "A direct jump from bats in the city of Wuhan is not very likely," said Ben Embarek.
On the origins
- "Our initial findings suggest that the introduction through an intermediary host species is the most likely pathway and one that will require more studies and more specific targeted research," said Ben Embarek.
- "The hypothesis of a direct spillover from an original animal source is also a possible pathway and is also generating recommendation for future studies," he said.
- "The findings suggest that the laboratory-incident hypothesis is extremely unlikely to explain the introduction of the virus into the human population," he said.
On the lab leak
- "We looked at what are the arguments for and against [the lab hypothesis]," said Ben Embarek. "We look at the fact that, nowhere previously was this particular virus researched or identified or known."
- "We were also discussing with managers and staff of many relevant laboratories in the region and looking and discussing with them this hypothesis," he said.
- "We also looked at the Wuhan Institute of Virology and the state of that laboratory ... and it was very unlikely that anything could escape from such a place," he noted.
On sampling other species of animal
- "Sampling of bats in Hubei province has failed to find evidence of SARS-CoV-2 in native viruses, and sampling of wildlife in different places in China has so far failed to identify the presence of SARS-CoV-2," said Liang.
- 11,000 samples from different kinds of animals like "pig, cow, goat, chicken, duck and goose" from 31 provinces in China across 2019 and 2020 and all were negative for SARS-CoV-2.
- 1,914 serum samples from 45 different species of wild animals, collected between November 2019 and March 2020, were all negative for SARS-CoV-2.
- 50,000 samples of wild animals covering 300 different species were tested via PCR and all tested negative for SARS-CoV-2.
China only agreed to an investigation into the origins after international pressure during the World Health Assembly in May 2020. Australia led the call for an independent inquiry into the origins, straining relations between the nations. Some scientists have suggested that while the investigative team has the expertise to trace the natural origins, it may not have the expertise for an investigation into a possible laboratory origin.
The press conference, which lasted just under three hours, didn't provide a whole lot of news and no data, but a full report is being prepared. It's uncertain when this will be ready. Ben Embarek made it clear the team has "been able to develop a series of recommendations for future studies." He said there is material, such as blood from blood banks, that might enable the team to get a better picture on the early days of the pandemic.