Piicture: 123RF/Piyamas Dulmunsumphun
Piicture: 123RF/Piyamas Dulmunsumphun

Melbourne/Brasilia/Zurich — The coronavirus probably spread from bats to humans via another animal, according to the long-awaited results of a joint World Health Organization-China study into the origins of Covid-19.

The most productive research would be to look for such an animal link, scientists said, after finding it improbable the virus resulted from a laboratory incident, according to the report. Future studies should be broadened to investigate susceptible animal species in China and elsewhere.

The findings confirm what researchers said in mid-February at the conclusion of their four-week mission to Wuhan, the central Chinese city where the first Covid cases emerged at the end of 2019, and in subsequent interviews. Possible intermediate host species include mink, pangolins, rabbits, raccoon dogs and ferret badgers, the report said.

“It supports our current picture of the start of the pandemic,” said Joel Wertheim, an associate professor of medicine at the University of California, San Diego, who reviewed part of the report. “From what I’ve seen, there was nothing shocking and unexpected in there.”

The hunt for the virus’s origin has been shrouded in controversy since the start of the pandemic, with China criticised for delaying access to scientists and Beijing and Washington pushing alternative theories about how Covid began.

WHO director-general Tedros Adhanom Ghebreyesus said on Monday all hypotheses are on the table and warrant complete and further studies. The expert team will brief WHO member-states on Tuesday before releasing the report publicly and briefing the media.

The was conducted by a team made up of both international and Chinese experts. The WHO has repeatedly said the report’s conclusions are independent and belong to the authors.

Pandemic prevention

While the search has become politicised, governments and scientists agree that deciphering the virus’s creation story is key to reducing the risk of future pandemics. The research was aimed at galvanising efforts to trace the origin of the virus that touched off the worst pandemic in more than a century, as well as its route of transmission to humans and the possible role of an intermediate animal host.

A spillover from bats via another animal is the most likely scenario in the report, followed by direct spillover. Introduction through frozen food was deemed possible, and a laboratory accident considered extremely unlikely.

Samples from bats and other animals in China did not test positive for the pandemic virus. The researchers recommended tracing the origin of SARS-CoV-2 worldwide in farmed and wild animals species likely to harbour coronaviruses, such as ferret-badgers, civets, mink and raccoon dogs, especially in areas where little research has been undertaken and where animal viruses are most likely to spill over to people.

Of 174 Covid-19 cases detected in Wuhan in December 2019, more than half had spent time in one or more produce markets in the city before being infected, according to the report. The Huanan market in central Wuhan, where animals and animal products were sold to the public, was linked to many early cases, though the researchers were not able to determine if it was the source of the initial transmission of the virus to humans or an amplifier of the early epidemic.

Market link

The market was identified early in the pandemic as a likely incubator of SARS-CoV-2, resembling the spawning in Guangdong province in 2002 of severe acute respiratory syndrome, or SARS, a bat-borne coronavirus that spread to civets and raccoon dogs before killing about 800 people.

Sales records showed 10 stalls at the Huanan market in late December sold animals or products from snakes, poultry, Sika deer, badgers, rabbits, bamboo rats, porcupines, hedgehogs, salamanders, giant salamanders and crocodiles. Farmed wildlife were sourced from 10 provinces, including three where related coronaviruses have been found in bats.

That provides a pathway by which the virus may have spilt over from wildlife into either people or animals farmed in southern China, and then shipped into a market by some means, Peter Daszak, a zoologist who was part of the joint research effort, said earlier this month.

Lab theory

The report noted that the Wuhan CDC laboratory moved in early December to a location near the Huanan market, and “such moves can be disruptive for the operations of any laboratory”.

However, the research centre did not report any disruptions or incidents that would have been caused by the move, and it was not storing or testing coronaviruses or bat viruses ahead of the outbreak, the report said.

The authors said that the three laboratories working in Wuhan on coronaviruses and vaccines had high biosafety levels and there was no evidence of Covid spreading among workers there.

The US government has questioned whether the WHO-convened experts were given enough access to reach a reliable conclusion. Top Biden administration officials on Sunday expressed concern about the way the WHO-China report was crafted, including the possibility that the Chinese government had a hand in writing it.

The US has “real concerns about the methodology and the process” of the report, including that the Chinese government “apparently helped to write it,” secretary of state Antony Blinken said.

China has been trying to deflect criticism of its handling of the pandemic amid growing scrutiny over the pathogen’s origins, including speculation promoted by the former Trump administration that the SARS-CoV-2 virus leaked from a Wuhan lab. It is unclear how much the report’s findings may persuade people convinced that the virus spread from a laboratory.

Beijing has suggested the virus may have arrived in China through refrigerated goods and has urged the WHO to carry out investigations in other countries.

Bloomberg

Would you like to comment on this article or view other readers' comments?
Register (it’s quick and free) or sign in now.

Speech Bubbles

Please read our Comment Policy before commenting.