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Early suspicions on pangolins and a laboratory, but scientists still convinced bats and animal market played key role in Covid-19

“The market had an animal there that amplified the virus and gave it to a lot of people, because of the first 48 cases, 26 were associated with the market. That rings alarm bells.”

Image: SIPA USA/PA Images

COVID-19 PUT the city of Wuhan in China on everyone’s lips. The first patients infected with pneumonia symptoms turned up at hospitals in that city in December. But the question of where the Covid-19 virus originated remains open.

The White House has pointed fingers at the Wuhan Institute of Virology, blaming it for an escape of the deadly virus into the city. Presumably, the suggestion is that scientists studying coronaviruses became infected and transmitted the virus to others outside the lab.

Significantly, in 2002-03, a new coronavirus caused the SARS outbreak, killing over 800 people. Scientists then went searching for similar viruses in wild animals. They visited caves in China and sampled bats and their droppings. The team, led by Chinese virologist Dr Shi Zhengli from the Wuhan institute, discovered bats chock full of coronaviruses, some remarkably similar to the SARS virus.

The suggestion is that similar coronaviruses being studied at the Wuhan institute escaped. There is no evidence for this lab escape theory. Instead, what research demonstrates is that coronaviruses are in wild animals and can jump to people on occasion.

The initial Covid-19 outbreak centred on a seafood market in Wuhan. This market sold not just seafood, but live farm animals and also wild animals for eating.

The market link set off alarm bells, because after SARS in 2003, mammals called palm civets sold in local food markets were found to harbour SARS virus. Scientists have searched for an animal that may have helped move the Covid-19 virus from bats to people.

Early on, suspicions fell on pangolins. This is one of the most illegally trafficked mammals, its scales sold for medicinal purposes. Virus hunter Dr Peter Daszak, president of EcoHealth Alliance, said: “I don’t buy the argument that pangolins are in any way involved. The native Chinese pangolin is almost extinct.”

He adds that dried pangolin scales are trafficked into China. “People don’t trade live pangolins,” he explained. It is therefore highly unlikely that any live pangolins were in the Wuhan food market.

When Chinese scientists entered the Wuhan market to investigate, they took samples from surfaces and animals there to test for genetic fingerprints of the Covid-19 virus.

“I am convinced that the market played an important role,” said Professor Lin-Fa Wang, scientist at the Duke Global Health Institute in Singapore, who is a leading expert on bat viruses. He is unsure where the outbreak started, but convinced that an animal in the market played its part. 

“The market had an animal there that amplified the virus and gave it to a lot of people, because of the first 48 cases, 26 were associated with the market. That rings alarm bells,” said Prof Wang.

China Centres for Disease and Control closed the market and took samples, but Prof Wang said that he thinks that this happened too late and that not every wildlife species sold there was still in the market. “Which is why they missed the chance to sample the animal,” he said.

“The market was highly contaminated,” added Prof Wang. “In one corner of the market, where the mammals were kept, they got almost 90% positive environmental swabs. They even isolated a live virus.” Though called the Wuhan Seafood Market, it traded all sorts of wild animals.

The virus may have jumped directly from bats to people, without an animal in between, according to Dr Daszak. Scientists had found a virus in a wild bat that has since turned out to be 96% similar to Covid-19 virus. Debate continues about whether the virus came directly from bats or via another mammal.

Dr Daszak pointed to a previous study with Prof Wang and Dr Zhengli which discovered that 3% of villagers in the south of China had antibodies against bat coronaviruses, meaning that these types of viruses infect people from bats – and it is not that rare an event. There is no need for a lab escape to explain the pandemic.

There may have been “other outbreaks, or people have died and it has not been noticed”, said Dr Daszak. What was probably missing was that they did not move from the first infected person to another. This also means that bat viruses could jump to people again in future.

Professor Wang in Singapore worked with Chinese colleagues such as Dr Zhengli in studying bat coronaviruses. They investigated an outbreak of coronavirus that killed 25,000 piglets in 2018, which came from bats. Again showing the potential of these types of viruses to make lethal jumps into new species.

This was reported in the scientific journal Nature in 2018, authored by Dr Zhengli in China, Prof Wang in Singapore and Dr Daszak in the US.

Wang described the discovery of the virus by medics in China as remarkable. “These were two clinicians, not scientists, but infectious disease doctors. They saw this severe pneumonia patient and thought it was unusual. So they sent this lung lavage specimen to a private sequencing company,” said Professor Wang. “Even in the US, Singapore and Australia, very few doctors would do that.”

The genetic sequence that came back pointed to a novel coronavirus as causing the mysterious illness.

Prof Wang said that before 20 January, China could have handled the situation much, much better.

“After 20 January, it is the international community that has failed,” he said.

Anthony King is a freelance science journalist working in Dublin. You can find him on Twitter @AntonyJKing

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About the author:

Anthony King  / Freelance science journalist in Dublin

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