The chances that Covid-19 emerged in Wuhan because of imported frozen food are "very low", international health experts said Monday, casting doubt on one of the main theories China has embraced for the cause of the first coronavirus outbreak in late 2019.
China has questioned the initial assumption the virus originated in the central city as it tries to deflect claims it mishandled the early outbreak, instead focusing on other potential causes as the country began to recover.
The "probability of a cold-chain contamination with the virus from a reservoir is very low," a team of World Health Organization-appointed and Chinese scientists said in a long-awaited report obtained by AFP before its official release.
It also said the introduction of the virus into China through frozen food would have been "extraordinary" in December 2019, given the virus had not been detected elsewhere at that time.
While there remained a "possible" chance of such a transmission, it said there was no conclusive evidence that frozen food played any role in the virus' spread.
The report instead concluded it is very likely Covid-19 first passed to humans from a bat through an intermediary animal, and all but ruled out a theory the virus could have leaked from a high-security lab in central China.
After the outbreak, explanations floated by Chinese officials and state-media have ranged from a conspiracy theory that US soldiers imported the virus in the 2019 World Military Games in Wuhan, to the frozen food theory after a series of outbreaks linked to workers who handled frozen goods.
- Introducing doubt-
The theory that the virus was originally imported into China could help Beijing in its battle against the criticism over the outbreak, experts say.
"The goal is probably to introduce enough doubt to make people question the origin of the virus," Adam Ni, analyst at the China Policy Centre in Canberra, Australia, told AFP.
At the same time, "there is this dynamic where the harder political leaders in some countries try to blame China for Covid-19, the harder that Beijing tries to put up counter-narratives," Ni said.
The nationalist Global Times published a report in December that asked in its headline, "Could cold chain imports have sparked Wuhan early Covid-19 outbreak?"
The newspaper drew a link between imported frozen and refrigerated food sold at the Huanan seafood market and the coronavirus, citing local scientists who called the theory "plausible" and "possible."
Meanwhile, local officials around the country have tested hundreds of thousands of imported food samples, publishing alerts whenever a sample tests positive for traces of the coronavirus.
- 'Bit of a leap' -
Despite reports in Chinese state media, there is still little evidence that coronavirus carried on cold-chain products can infect humans, scientists say.
Chinese researchers have said outbreaks among Beijing market workers and dock workers in eastern China's Qingdao were linked to virus particles on frozen fish.
The WHO report also said the only epidemiological link which could be established in the Qingdao cases "was exposure to [the virus] on the surface of cold-chain packaging."
"There's a remote possibility that something could happen," Richard Sugrue, a virologist at Nanyang Technological University in Singapore told AFP.
But Sugrue said "it's a bit of a leap to say that (as) this has been detected in frozen food that that could be a route of transmission."
Leong Hoe Nam, an infectious disease specialist at Singapore's Mount Elizabeth Novena Hospital, agreed that it was unlikely cold-chain imports could have sparked the initial outbreak in Wuhan.
"Cold chain food is still being brought into China, Singapore, Taiwan and all other countries with a good control of the virus," Leong told AFP.
"And yet it happens only in two places in China."