All hypotheses on how the Covid-19 pandemic began remain open, the World Health Organization said Friday, following an inconclusive four-year investigation that was hamstrung by crucial information being withheld.
The global catastrophe killed an estimated 20 million people, according to the WHO, while shredding economies, crippling health systems and turning people's lives upside-down.
The first cases were detected in Wuhan in China in late 2019, and understanding where the SARS-CoV-2 virus that causes Covid came from is seen as key to preventing future pandemics.
However, a lengthy investigation launched by the UN's health agency said that pending further data, the origins of Covid and how it first spread would remain inconclusive.
"As things stand, all hypotheses must remain on the table, including zoonotic spillover and lab leak," WHO chief Tedros Adhanom Ghebreyesus told a press conference, referring to the two main hypotheses as to how the pandemic began.
Expert investigation
After much delay, a WHO team of experts went to Wuhan in January 2021 to look into the origins of the virus in cooperation with their Chinese counterparts.
Their March 2021 joint report concluded that the most likely hypothesis was that the virus jumped from bats to humans via an intermediate animal.
They also deemed the theory that it might have escaped from Wuhan's virology laboratories "extremely unlikely".
However, that investigation faced harsh criticism for lacking transparency and access, and for not evaluating the lab-leak theory seriously.
Tedros launched another investigation, setting up the Scientific Advisory Group for the Origins of Novel Pathogens (SAGO) in July 2021.
The report by the group of 27 experts was published on Friday.
"Until further requests for information are met, or more scientific data becomes available, the origins of SARS-CoV-2 and how it entered the human population will remain inconclusive," SAGO chair Marietjie Venter said at the press conference.
She added that it was "not yet clear" if the Wuhan seafood market was where the virus first spilled over into humans.
As for lab leak theories, she said much of the information needed to assess this hypothesis had not been made available, so it "could not be investigated, or excluded".
'Crucial question'
"Over the past five years, we have learned a lot about Covid-19 but there is one crucial question about the pandemic that we have not yet answered: how it started," Tedros said.
He said SAGO had advanced understanding of the origins of Covid-19 but much of the information needed to evaluate fully all the hypotheses had not been provided.
"Despite our repeated requests, China hasn't provided hundreds of viral sequences from individuals with Covid-19 early in the pandemic, more detailed information on animals sold at markets in Wuhan, and information on work done and biosafety conditions at laboratories in Wuhan," he said.
"WHO is also aware of intelligence reports performed by other governments around the world on the origins of Covid-19. We have also requested access to those reports."
US President Donald Trump's administration has officially embraced the lab leak theory.
Tedros said finding out how Covid-19 started was a moral imperative for the sake of those who lost their lives in the pandemic.
He also said the virus was continuing to evolve, take lives and leave people suffering with post-Covid conditions, or so-called long Covid.
Tedros said the WHO continued to appeal to Beijing and other countries with information about the origins of Covid-19 to share the information openly, in the interests of protecting the world from future pandemics.
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