Home/ News / World/  In hunt for Covid-19 origin, WHO team focuses on two animal types in China

World Health Organization investigators are honing their search for animals that could have spread the new coronavirus to humans, identifying two—ferret badgers and rabbits—that can carry the virus and were sold at a Chinese market where many early cases emerged.

Members of a WHO team probing the pandemic’s origins say further investigation is needed into suppliers of those and other animals at the market, some of which came from a region of China near its Southeast Asian borders where the closest known relatives of the virus have been found in bats.

Team members say they have yet to establish all the creatures sold, legally or illegally, live or dead, at the market in the Chinese city of Wuhan that was tied to the first known cluster of cases in December 2019.

China’s National Health Commission and foreign ministry declined to comment.

The WHO team is juggling multiple competing hypotheses and still isn’t sure if the virus first jumped from animals to humans at the market or if it was circulating elsewhere first. But working with the available evidence, they are gaining a stronger understanding of which animals could have plausibly been vectors.

WHO investigators also want China to conduct widespread testing of its mink farms, following the discovery that the virus had spread back and forth between mink and humans in Europe.

Continuing uncertainty over how, when and where the virus first spread to humans is feeding international tensions, with the U.S. and China trading accusations that they are hindering the WHO’s investigation.

The WHO team recently made a four-week trip to Wuhan, after months of negotiation, but its access to local scientists and their data depended on cooperation from Beijing, which has repeatedly suggested the virus originated outside China.

The market remains a focus of the probe because it was tied to the earliest known cluster of infections and because WHO scientists believe the virus most likely originated in bats and spread to humans via another animal, possibly on a farm or at a market. Many scientists have suggested that the virus could have spread via China’s illegal wildlife trade.

Peter Daszak, a zoologist on the WHO team, said in an interview that ferret badgers were among carcasses found in freezers at the market, and that while they tested negative, they were capable of carrying the virus.

“It provides a pathway for how the virus could have gotten into Wuhan," Dr. Daszak said.

Ferret badgers, which live mainly in southern China, are from the same family of mammals as weasels and otters, and they are often hunted and traded for food or fur, despite being a protected species.

Dr. Daszak said rabbits were also present in the market, and they “turn out to be quite susceptible to SARS-CoV-2."

Marion Koopmans, a Dutch virologist on the WHO team, also identified ferret badgers and rabbits as the animals there that are thought to be capable of carrying and spreading the virus.

Identifying the animal that likely first infected a human is a critical step in the investigation as it could help to trace the virus to its original reservoir, most likely a bat colony, and help prevent it from spreading again to humans, scientists say.

Dr. Daszak said supply chains for the 10 stalls selling wild animals in the market included wildlife farms in the southern Chinese provinces of Guangdong, Guangxi and Yunnan, which borders Vietnam, Laos and Myanmar.

That was a critical finding, he said, because two close viral relatives of SARS-CoV-2 were found in bats in Yunnan province. And pangolins—scaly, ant-eating mammals—with similar viruses were found in Guangxi and Guangdong provinces.

But he and other team members said that the investigation needed to look also at other countries, especially in Southeast Asia, where similar coronaviruses had recently been found, including Thailand and Cambodia.

“I do think it’s quite feasible that an animal could have come across the border," he said. “It’s also possible that a frozen carcass could have been shipped over."

Although the virus can survive for long periods when chilled or frozen in laboratory experiments, it is also weakened when frozen and thawed and it’s unclear whether it remains infectious afterward, many scientists say.

The WHO team still didn’t know if other animals that could carry the coronavirus, including civet cats and raccoon dogs, were actually sold at the market, team members said.

They also said they had tried in vain to establish whether there were live mammals there. Dr. Daszak said during the Wuhan mission the team was told repeatedly there weren’t. “We don’t know if that’s true," he said, adding that vendors could have been selling wildlife illegally.

Former vendors, and the manager of a company that began disinfecting the market shortly before it closed on Jan. 1, 2020, have told The Wall Street Journal they saw carcasses and caged live mammals, including dogs, rabbits and badgers.

WHO and other scientists say any infected animal or meat might have been sold weeks earlier or removed from the market before Chinese authorities arrived, especially if it was illegal wildlife.

Chinese authorities who started taking samples from the market on Dec. 31, 2019, say they found traces of the virus in environmental samples taken from sewers, stalls and other surroundings, but not in any of the animal specimens.

Liang Wannian, the head of a Covid-19 expert panel of China’s National Health Commission, said last week there were no positive results in antibody tests on 1,914 samples from 35 different species of wild animals, and in PCR tests—which detect genetic material from the virus—on 50,000 samples from 300 different wildlife species in China.

Dominic Dwyer, an Australian microbiologist on the WHO team, said in an interview that it makes sense to include Southeast Asian and other countries in the search. “But it doesn’t mean that there’s an interpretation that that’s exactly where it came from, or that it didn’t come from China," he added.

Dr. Dwyer said more work needed to be done to establish exactly what animals were sold at the Wuhan market, legally and illegally.

“Just because a wildlife trade is illegal, doesn’t mean it doesn’t happen, and that’s tricky," he said. “They’ve got to avoid the kind of thought process of saying it’s illegal therefore it wouldn’t have happened. You’ve still got to follow these things up."

He and other team members also said that China needed to conduct widespread testing of its mink farms, even though they are mostly in its north. “China hasn’t reported any mink outbreaks, and I think that’s an area they need to do some work over," Dr. Dwyer said.

Dr. Koopmans said that the virus spreads too quickly through mink to make it an ideal reservoir for the virus, though closer examinations of newborn mink, whose immune systems respond differently, could potentially change that assessment.

Peter Ben Embarek, the WHO team leader, said in an interview published in Science magazine on Sunday that investigators wanted to do more systematic studies, particularly in China, on other animals susceptible to SARS-CoV-2, including minks, foxes and raccoon dogs.

He and other team members also said it was unlikely that the virus first entered Wuhan—as Chinese officials suggest—via other kinds of frozen food imports because there were no widespread Covid-19 outbreaks in food factories elsewhere in the world at the time.

This story has been published from a wire agency feed without modifications to the text

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