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Since the coronavirus pandemic was unleashed across the globe, much of the world's attention zeroed in on a wet market in the port city of Wuhan, China.
However Australian scientist Dominic Dwyer, who was among a World Health Organisation team of researchers sent to China to investigate the origins of the virus, says it did not necessarily stem from the live animal market.
"The market in Wuhan, in the end, was more of an amplifying event rather than necessarily a true ground zero. So we need to look elsewhere for the viral origins," he wrote in a new piece for The Conversation, detailing the highly publicised envoy.
"Our investigations concluded the virus was most likely of animal origin. It probably crossed over to humans from bats, via an as-yet-unknown intermediary animal, at an unknown location.
"But we are still working to confirm the exact chain of events that led to the current pandemic. Sampling of bats in Hubei province [where Wuhan is located] and wildlife across China has revealed no SARS-CoV-2 to date," he wrote.
The team visited the now closed market site, but Professor Dwyer noted that none of the animal products sampled after the market’s closure tested positive for the virus.
While some viral sequences from several patients linked to the market were identical, suggesting a transmission cluster, there was some diversity implying other unknown chains of transmission that weren't sampled, according to investigators.
The precise origins of the coronavirus pandemic will likely never be known, and Prof Dwyer's remarks echo others who were involved with investigating the origins of the pandemic, who have said China "is by no means necessarily the place where the leap from animals to humans took place".
China has faced criticism about not being fully transparent with certain case data related to early virus patients, including from members of the Australian government who have accused it of having "something to hide".
With a report from the WHO team due in the coming weeks, "investigators will also look further afield for data, to investigate evidence the virus was circulating in Europe, for instance, earlier in 2019," Prof Dwyer wrote.
'Cold chain' virus theory lingers
Prof Dwyer, who is a microbiologist at Westmead Hospital in Sydney, said another theory which implicates the role of frozen food in the origins of the virus jumping to humans couldn't be ruled out – an idea referred to as the "cold chain hypothesis".
The notion posits that the virus could have originated somewhere else in the food supply chain such as via farming, processing, transporting or freezing of food.
"It’s unproven that this triggered the origin of the virus itself. But to what extent did it contribute to its spread? Again, we don’t know," Prof Dwyer said.
"Environmental sampling in the market showed viral surface contamination. This may indicate the introduction of SARS-CoV-2 through infected people, or contaminated animal products and 'cold chain' products."
Further investigation in this area is being conducted.
He also noted that the theory positing the virus escaped from a nearby lab was "extremely unlikely".
The WHO team are due to publish their official report in the coming weeks, while more data will be collected further afield from China.
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