GENEVA: Covid-19 probably passed to humans from a bat via an intermediary animal, an international expert mission to China concluded in a report seen on Monday, 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 seen as "extremely unlikely", according to a copy of the long-awaited final report obtained by AFP before its official release.
Drafted by a team of World Health Organization-appointed international experts and Chinese counterparts, the report has been keenly anticipated ever 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 more than 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.
Ahead of a meeting with world leaders, UN chief Antonio Guterres called for more debt relief for the poorest countries struggling with a slump in activity caused by the pandemic.
And in Europe, vaccine front-runner Britain enjoyed a taste of freedom with a new stage of rolling back restrictions, as neighbours like France and Germany wrangle over how to slow rising cases.
But new hope was on offer from Johnson & Johnson, which said it would begin delivering its single-shot vaccine to Europe on April 19 and to Africa in the second half of the year.
The expert report on Covid has had a troubled birth, with publication delays adding to the hold-ups and 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 January 14 this year, 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 punishing anti-virus measures.
People in Britain rushed to pools and parks on Monday to enjoy newfound freedoms, with the government allowing small groups to gather and sports activities to resume.
"We haven't swum since January 5 so we were beyond excited to come back and get back into the water," swimmer Jessica Walker told AFP at a pool in London.
The country is also lining up an FA cup semi-final football match in April as a test run for reopening large events.
With fewer confirmed cases, some African economies have nevertheless been hobbled by coronavirus restrictions, making Johnson & Johnson's announcement of a deal with the African Vaccine Acquisition Trust (AVAT) welcome.
AVAT has an initial deal for 220 million doses of the single-shot vaccine -- said by the company to protect against regional variants -- with J&J subsidiary Janssen Pharmaceutica for delivery from the third quarter of this year, with an option on 180 million more.
With EU approval already in its pocket, the US drugmaker also plans to begin European deliveries on April 19.
The bloc has lagged far behind Britain in its vaccine rollout, and the latest rises in cases have seen German Chancellor Angela Merkel lay into state leaders including her own party colleagues over reintroducing restrictions.
In neighbouring France, President Emmanuel Macron may announce new measures this week after partial, regional shutdowns failed to keep the number of people in intensive care below its second-wave peak.
Also on Monday, the makers of the Russian-developed Sputnik V shot struck a deal with a Chinese firm to make more than 60 million doses, with the jab's backers highlight a "rising demand" for the drug.
As he prepared to meet dozens of national leaders, UN Secretary-General Antonio Guterres said a "new debt mechanism" allowing for options like debt swaps, buy-backs and cancellations was needed to help worse-off countries.
The pandemic has pushed the world to "the verge of a debt crisis" requiring "urgent action", Guterres said.
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", 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 candidates 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 former US president Donald Trump's administration that the virus escaped from a research lab were judged "extremely unlikely". But in Geneva on Monday, WHO boss Tedros Adhanom Ghebreyesus stressed that "all hypotheses are open, from what I read from the report... and warrant complete and further studies".