Covid-19 probably passed to humans from a bat via an intermediary animal, an international expert mission to China has concluded in a report, with investigators all but ruling out a laboratory leak.
The intermediate host hypothesis was deemed “likely to very likely”, while the theory that the virus escaped from a lab was considered “extremely unlikely”.
Drafted by a team of World Health Organization-appointed international experts and their Chinese counterparts, the report has been keenly anticipated since investigators left China more than a month ago.
But it does not offer definitive answers on the mystery at the very heart of the pandemic: how the virus that causes the disease first jumped to humans.
Covid-19 has killed about 2.8 million people worldwide in the 15 months since it emerged, forcing governments around the world to introduce punishing restrictions that have pummelled the global economy.
The expert report on Covid has had a troubled birth, with publication delays adding to the hold-ups, after diplomatic wrangling that plagued the WHO’s attempts to get experts into Wuhan, the city at the centre of the initial outbreak.
They arrived on 14 January, more than a year after the first cases surfaced. In that time, vaccines have offered a glimmer of hope and allowed some countries to emerge from more than a year of anti-virus measures.
While societies continue to battle the effects of the pandemic, there is still little clarity over its origins. The WHO report left “not everything answered” but was “surely a good start”, the Dutch virologist and team member Marion Koopmans tweeted.
Experts believe the Sars-CoV-2 virus that causes the Covid-19 disease originally came from bats. The report authors offered a ranked list of possible ways it could have made the jump to humans, calling a direct leap “possible to likely” and a scenario with an intermediate animal “likely to very likely”.
Experts named candidate animals including mink, pangolins, rabbits and ferret badgers.
Beijing’s pet theory that the virus did not originate in China at all but was imported in frozen food was judged “possible” but very unlikely.
Meanwhile, claims promoted by the former US president Donald Trump’s administration that the virus escaped from a research lab were judged “extremely unlikely”. But in Geneva on Monday, the WHO boss, Tedros Adhanom Ghebreyesus, said: “All hypotheses are open, from what I read from the report … and warrant complete and further studies.”