Beijing — With just days left in their month-long visit to Wuhan, the World Health Organization’s team of COVID-19 experts co-hosted their first press conference on Tuesday to share some key findings from the hunt for the coronavirus’ origin. The biggest takeaway from the nearly three-hour event was that the scientists believe it’s “extremely unlikely” a lab-related accident was the source of the pandemic, and all current evidence “continues to point to a natural reservoir.”

The next step, said WHO lead investigator and food safety expert Peter Ben Embarek, would be to “look at the possible pathways of introduction of the virus into the human population,” and for any evidence that it might have made that jump into humans earlier than currently known.

After weeks in Wuhan, the team was still unable to answer the overarching question of where COVID-19 came from.

“From the early days of December 2019, did we change dramatically the picture we had beforehand?” Ben Embarek, a Dutch food safety expert, asked rhetorically. “I don’t think so. Did we improve our understanding? Did we add details to that story? Absolutely.”

Virologist Marion Koopmans, also of the Netherlands, and Liang Wannian of China’s National Health Commission spoke on stage to discuss methodology and results at the briefing, which was broadcast on television and social media around the world. 

Speaking for the WHO’s international team, Ben Embarek laid out four hypotheses about COVID-19’s origin and said the “most likely pathway” in the scientists’ view was that the virus spread to humans through an intermediary species that lives close to human populations. He said that theory, like the others, “will require more targeted research.”

Less likely but “still possible” is the notion that the coronavirus jumped directly from a primary source animal into humans. Many scientists believe COVID-19 originally came from certain species of bats, but they aren’t easily found in Wuhan.

A third hypothesis is “food chain” transmission, with the virus originating elsewhere and then riding into central China on the surfaces of cold-chain frozen food packaging.

The least likely theory, according to the WHO team, is a lab-related incident, but the scientists said that was “not a hypothesis that would imply future study into the origin of the virus.”

“Accidents do happen,” admitted Ben Embarek when challenged on why a laboratory — such as the often-mentioned Wuhan Virology Institute — had been ruled out as the source of the virus. He said there had been “no reports” of this coronavirus or one closely linked to it being worked on in any lab in the world.

He stressed that “it was very unlikely anything could escape” from the maximum biosecurity facility in Wuhan, and lab accidents in general, he said, “are extremely rare events.”

During the course of the WHO’s month-long stay in China the team has pushed for access to new evidence, and they did visit now well-known sites including the Huanan seafood market, once believed to be ground zero, along with the Wuhan Institute of Virology and hospitals that treated the first coronavirus patients. 

Whenever new information becomes available, said WHO expert Koopmans, “we can take this again and say, ‘okay, with this new information does our assessment of these different entry pathways change?”

“That could be anytime, because there are ongoing studies in different parts of the world,” Koopmans noted.

As the WHO’s allotted time window in China — they got one-month visas — winds down, the scientists stressed that there could still be years of investigation left to do before the COVID-19 origin is determined, if it ever is.

The WHO team’s visit was delayed for months by Chinese officials, who never offered any real explanation.

Only journalists physically in Wuhan at the event on Tuesday were allowed to ask questions of the WHO team. The press conference was only announced early on Tuesday morning. Face-to-face interviews — even socially distanced — with members of the international team were not permitted.