Picture: REUTERS
Picture: REUTERS

A World Health Organisation (WHO) investigation in China found that the coronavirus most likely jumped to humans through an animal host or frozen wildlife products, finding that it’s “extremely unlikely” it came from a laboratory leak.

No further research is needed to look into the theory about a leak, Peter Ben Embarek, a WHO official, told reporters on Tuesday at a joint briefing with China in Wuhan, the city where Covid-19 first mushroomed at the end of 2019. That speculation had been promulgated by former US president Donald Trump and some others.

The virus could have been introduced to the Huanan wet market in Wuhan, which many of the first Covid-19 patients were linked to, by a person who was infected or by a product that was sold there, Ben Embarek said.

“Among the more interesting products were frozen wildlife animals,” he said. “Some of these species are known to be susceptible to these kinds of viruses.”

The highly anticipated mission followed months of negotiation with a defensive China to facilitate and co-operate with the probe. Stung by criticism that it initially covered up the extent of the crisis, Chinese state media and officials have promoted the theory that the virus didn’t start in China, but was brought in. The WHO’s validation of a potential cold-chain transmission route is likely to bolster those efforts.

The team also examined tens of thousands of patient samples from Wuhan prior to the emergence of sick people in 2019. There was no evidence of significant outbreaks in the country before December 2019, WHO officials said.

“We embarked on a very detailed and profound search for other cases that may have been missed early on in 2019,” said Ben Embarek. “The conclusion was we did not find evidence of large outbreaks that could be related to cases of Covid-19 prior to December 2019 in Wuhan or elsewhere.”

The panel, comprising 17 Chinese and 17 international experts, looked for clues to understand how SARS-CoV-2 — whose closest known relative came from bats 1,600km away — spread explosively in Wuhan before causing the worst contagion in more than a century. Finding the source will inform efforts to stop the virus, and other pathogens with pandemic potential, spilling over into human populations.

Worldwide, Covid-19 has caused more than 106-million infections and 2.3-million deaths.

Mission delegates worked in three groups that focused on the epidemiology or spread of the disease, the potential involvement of animals and the environment, and the molecular evolution of the virus.

Researchers found a coronavirus related to SARS-CoV-2 in bats at a wildlife sanctuary in Thailand, according to a study released on Tuesday in the Nature Communications journal, another indication of how widespread such viruses are. While highly similar to the coronavirus that causes Covid-19, the Thai version doesn’t appear to be adapted to spread in humans by the same mechanism, researchers from Thailand and Singapore said in the report.

Scientists still do not understand if the virus can spread to humans after persisting in frozen conditions, and how that would occur, according to Ben Embarek. More work was needed to study that possible path and trace the source of animal products, he said.

“It’s interesting to explore if a frozen wild animal that was infected could be a potential vehicle for the introduction of the virus into market environments where we know the temperature, humidity, environment could be conducive to rapid spread of the virus,” he said.

The lack of a clear pathway from bats to humans had stoked speculation — refuted by many scientists — that the virus might have escaped from the Wuhan Institute of Virology, home to a maximum bio-containment laboratory that studies bat-borne coronaviruses.

Members of the WHO mission visited the lab last week and asked Shi Zhengli, who has collected and analysed these viruses for more than a decade, about the research and the earliest known coronavirus cases.


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