The wildlife trade in China is the most likely pathway through which Covid-19 was able to spread from the original animal source, possibly bats, to humans, according to one of the authors of a long-awaited World Health Organization report on the origin of the virus.
The report, expected to be released on Tuesday after repeated delays, will include “multiple hundred pages, with lots of data, lots of new facts and information,” said Peter Daszak, a member of the WHO team of international experts who visited the Chinese city of Wuhan, where the virus first emerged, earlier this year.
But the report’s main conclusions – about the possible ways in which the novel coronavirus could have emerged in Wuhan – will remain unchanged from when the WHO wrapped up their trip in February, he said.
The WHO investigation, conducted more than a year after the initial outbreak, has been under intense scrutiny since the outset. Some scientists and governments have questioned the independence of the study. Beijing, on the other hand, has accused Washington and others of “politicizing” the origin of the virus.
Last week, the Chinese Foreign Ministry gave a briefing to diplomats on the main findings of WHO’s research in anticipation of the release of the report.
Feng Zijian, deputy director of China’s Center for Disease Control and Prevention and a member of the Chinese team, said the experts on both sides examined four possibilities of how the virus got to Wuhan – through frozen food, directly infecting a human, infecting an intermediate animal and leaking from a laboratory.
Feng said the experts agreed that is was most likely that the virus had jumped to humans via an intermediate host, and that it is “extremely unlikely” that the virus had leaked from a lab.
According to Daszak, Chinese and international experts agreed that the most likely path the virus took was from an original bat host, which then infected an intermediary in southern China’s wildlife farms. Those animals were then sold to a Wuhan wet market, which is thought to have played a central role in the spread of the disease.
The Huanan Seafood Wholesale Market was where a cluster of pneumonia-like cases were first detected in December 2019. It was shut down by Chinese authorities on January 1, 2020 for disinfection, and has been closed to the public since.
On the ground in Wuhan, Daszak and other WHO experts visited the Huanan market and found that it not only sold seafood, but also “wildlife and wildlife products, whole carcasses of animals and live animals of different types” from farms across China.
“So there was definitely a pathway that takes animals coming into that market from all over China, including the places where the nearest relatives of SARS-CoV-2 have been found in bats,” said Daszak, a British zoologist who studies viral origins in animals and president of EcoHealth Alliance, an environmental health non-profit.
The closest known relative of the coronavirus causing Covid-19, known officially as SARS-CoV-2, was previously discovered in horseshoe bats, in China’s southwestern Yunnan province, in 2013. Other coronaviruses closely related to SARS-CoV-2 have also been discovered in frozen bat samples in Cambodia and Japan.
“So what we found, I think, is pretty important evidence of a way the virus could have emerged from rural China into a big city like Wuhan and led to an outbreak,” Daszak said. “And it turns out that at the end of the report, both the China team of experts and the WHO experts all felt this was the most likely pathway that the virus took. We considered this likely to very likely, as a way that this virus would have emerged.”
The WHO team was not the first group of scientists to have surveyed the Huanan market. During the initial outbreak in Wuhan, Chinese scientists also went there. But by the time they got there, the market was closed and most of the live animals had already been taken out, Daszak said.
Nevertheless, the Chinese scientists took as much evidence as they could and swabbed over 900 samples, including environmental samples. But all of the animal carcasses they found tested negative for the virus, according to Daszak.
The report also lays out a series of recommendations on what needs to be done to find out more about the origin of the virus, from both the Chinese and the WHO sides.
One key recommendation, following the identification of the potential pathway through wildlife farms, is to go to those farms and interview the owners, their relatives and test people to look for evidence on whether they were infected with Covid-19 earlier than the first known patients in Wuhan, Daszak said.
Researchers should also find out what animals these farms supplied and where they came from, and test animals around the farms to search for “evidence of the virus being there in the wild,” he added.
“The next step is to start that work, and we’re already lining up the conversations with our China counterparts to begin that process,” he said. “This report is really just the beginning.”