Research into wildlife farms in southern China will be a critical next step in the search for the origins of Covid-19, a member of the WHO investigation team has said.
Biologist and food safety and disease expert Hung Nguyen-Viet was one of the 10 international scientists who took part in the 28-day mission to Wuhan to understand how the virus began spreading in humans before it was identified in that city in late 2019.
The team’s findings, a joint report with Chinese scientists, have come under scrutiny after they were published on Tuesday, with World Health Organization director general Tedros Adhanom Ghebreyesus saying the team did not have full, timely access to data.
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Nguyen-Viet, who is Vietnamese but based in Nairobi where he co-leads the animal and human health programme at the International Livestock Research Institute, said the international interest around the research was like nothing he had experienced in this career.
“We were aware that we conducted this mission amid political sensitivities, but we focused on the research, on the mission purpose and the work we were asked to do,” he said.
As for whether there were restrictions on access to data during the mission, Nguyen-Viet said some data was still being compiled and processed.
“It’s an evolving process and that is understandable,” he said.
Nguyen-Viet, who was on the mission’s animal and environment team, said a critical focus for his group was understanding the role of the Huanan Seafood Wholesale Market, which has been linked to a number of the first detected cases in Wuhan.
Of the 174 cases of Covid-19 identified in December 2019, 28 per cent had a connection to the market, but over half had exposure to markets in general.
It is still not clear if the Huanan market was where the virus was introduced to humans or if the disease spread quickly there after being brought in by an infected person. However, the WHO team believes the virus originated in bats and it was very likely it had been passed to humans via an intermediary animal.
The team also said direct transmission to humans from bats or other animals was also a likely scenario, while it was possible the virus had been spread via cold chain products. However, the investigators concluded it was extremely unlikely that it had leaked from a laboratory studying bat viruses.
Nguyen-Viet said that the data gathered by Chinese researchers and analysed by the two sides had provided a potentially critical clue. Some of the goods sold in Huanan had come from southern Chinese provinces that are known to harbour bats that carry viruses which are closely related to the one that causes Covid-19.
“We didn’t have this kind of information before we came to China …. and this shows a potential pathway [for the virus] from wildlife farms in southern China to Wuhan,” he said.
“But the full picture was not there, so that’s why the recommendation is really to understand how this wildlife was farmed, how people were exposed to the wildlife and also to explore if these animals are exposed to bats or other wild animals – because that type of interaction might play a role in the emergence of the Sars-CoV-2 virus,” he said.
Outside scientists have expressed surprise that such work was not already done by China’s scientists over the past year, especially as the country in February 2020 banned the trade of wildlife for consumption, resulting in farm closures.
These studies may not have been done yet due to time constraints, as China focused on disease control and environmental research was going on in various areas, according to Nguyen-Viet.
He also said it was not clear to him whether the farms in those regions would have already been shut down.
“But I think that we need to pursue this direction to see how this law is actually implemented and enforced, maybe this wildlife farming still exists – we need to see and ask questions,” he said.
But whether this gets done, and by whom, remains to be seen.
“The mission is completed and the report is handed over, and phase two depends on how the WHO works with China,” Nguyen-Viet said.
Meanwhile, research released this year from teams in Cambodia and Thailand has found viruses that were closely related to Sars-CoV-2.
However, its closest relative remains a bat virus found in southwestern China, and none can be considered a direct ancestor.
“I would say that the focus still needs to be in China, because of links to Wuhan and the information [about southern farms] that we found. But at the same time, we need to target some of the hotspot countries where we have the early evidence that the virus could come from there,” Nguyen-Viet said.
“I think that is going to be a crucial step to pursue to understand more.”
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