In the wake up of the civilization Health organization’s investigation, there space still an essential questions about when, where and how the pandemic began.

WHO investigators visit website in China as component of your probe right into the pandemic’s origins.Credit: Hector Retemal/AFP/Getty

Following a month-long fact-finding mission in China, a civilization Health organization (WHO) team investigating the origins of the COVID-19 pandemic concluded that the virus more than likely originated in bats and also passed to world through an intermediate animal. But basic questions remain around when, where and also how SARS-CoV-2 very first infected people.

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As the global WHO team finalizes a report that its findings, i beg your pardon is expected next week, speaks to four of the investigators about what lock still want to know.

Was the virus circulating in Wuhan prior to the very first known cases?

To map the virus’s origin, it’s vital to pin down exactly when the an initial cases arisen in people. The that team established that the very first person well-known to have actually COVID-19 to be an office worker in Wuhan through no recent travel history, who began showing symptoms on 8 December 2019, claims Peter Ben Embarek, a food-safety scientist in ~ the that in Geneva, Switzerland, who led the investigation. But the virus was probably spreading in the city before that, since it to be well-established by later that month, he says.

Yet proof of earlier spread has actually proved elusive. Researcher in China conducted substantial survey of patient reports indigenous hospitals in Wuhan made between October and also December 2019, and identified fewer 보다 100 people who had actually symptoms the COVID-19. They climate tested the blood that 67 that those human being for antibodies generated by previous infection v SARS-CoV-2, but found none. This argues there no a large cluster the infections before December, or an inexplicable spike in deaths in the surrounding province of Hubei.

‘Major stones unturned’: COVID beginning search must continue after that report, speak scientists

But Ben Embarek says the analysis should be recurring using much less restrictive symptom criteria, to make certain that researchers spot every potential COVID-19 cases.

Scientists in China should also search for evidence of past infection in part 200,000 archived samples right now held at the Wuhan Blood Center and also in various other regions throughout China, claims team member Dominic Dwyer, a clinical virologist at brand-new South Wales health Pathology in Sydney, Australia. This would show whether the virus was spreading in the general populace in China — not just amongst people that went to health facilities — before December 2019.

Some scientists not associated in the WHO investigation have currently looked in ~ blood-bank samples taken as much as a year prior to the pandemic, in Guangzhou, southerly China. (Close family members of SARS-CoV-2 have actually been found in bats and pangolins in southerly China.) few of the samples tested positive for antibodies versus SARS-CoV-2, yet Ian Lipkin, an infectious-diseases researcher at Columbia university in brand-new York City, who worked on the analysis, claims the test was not certain enough to say for certain that the antibodies weren’t caused by epidemic with other viruses. “There is a many laboratory work that needs to be done the hasn’t to be done,” says Lipkin, who also wants to understand whether there are autopsy samples from prior to December 2019 that can be studied because that traces of viral genetic material.

Was the virus spreading in people outside China prior to December 2019?

Answering this inquiry is also an essential to creating the timeline that the an initial COVID-19 cases. Previously, researcher in Europe have reported1,2,3 detect antibodies against SARS-CoV-2 in samples taken at blood banks from November 2019 onwards.

Ben Embarek states this doesn’t necessarily indicate the virus source in Europe, but supports the idea the it was spreading in Wuhan prior to the first known cases. “Wuhan at that time to be a very well-connected international city with straight flights come the entire planet top top a daily basis. Therefore if it was circulating in Wuhan, it can easily have actually been carried to various other parts of the world through travellers, and circulating again, undetected, in various regions,” he says.

Still, that recommends the the blood samples from Europe it is in retested to check that they indicate instances of COVID-19. Several of them, indigenous Italy and also France, are currently being reanalysed, that says.

What to be the duty of the Huanan market?

The intermediate animal that happen the virus native bats to human being has no been identified, yet researchers think it could be a wild varieties that is sold as food in ‘wet markets’, which generally sell live animals. Early in the pandemic, investigators homed in ~ above the Huanan Seafood market in Wuhan, since it sold fresh and also frozen animals and also many the the earliest infections were in civilization who had visited it. But the command went cold as soon as other early cases were found that to be not linked with the market. Viral product was determined in drains and sewage at the market, yet none was discovered on any pet carcasses.

Still, the sector is the only place where a big number the the civilization infected at the start of the outbreak were exposed to meat and animals. It’s essential to establish how the virus acquired into the market and whether it was on one animal, states WHO team member Hung Nguyen-Viet, one environment and food-safety researcher at the global Livestock research Institute in Nairobi.

Nguyen-Viet states the team figured out ten stalls selling wildlife, either wild or farmed, that could have lugged the virus into the sector from ranches in southerly China. Part wild animals sold for meat, such as rabbits and also ferret-badgers, are susceptible to SARS-CoV-2 or the connected virus that reasons severe acute respiratory syndrome (SARS).

WHO team member Peter Daszak, president of the non-profit research company Ecohealth Alliance in brand-new York City, states the farms should it is in investigated to see whether there were infections in the animals or amongst workers. He also wants to recognize what pets were marketed in other Wuhan markets. When the team interviewed the an initial person well-known to have actually COVID-19, he stated that his parents had actually visited a local ar wet market, states Daszak.

Did frozen wild-animal meat have actually a role in the early on spread the the virus?

The that team concluded that it’s most most likely the virus jumped indigenous live pets to people, yet Ben Embarek states it is possible the virus gone into the Huanan industry through infected frozen wild pets from ranches in southern China, and also then sparked an outbreak. Daszak marvels whether frozen ferret-badgers sold at the market can have carried the virus. “These were carcasses skinned at the market, not simply cubes that meat in a plastic packet,” the says.

Can COVID spread out from frozen wildlife? researchers probe pandemic origins

Although researchers in China have likewise isolated viral RNA indigenous the packaging of imported frozen fish4, Ben Embarek states the who team concluded the these items were not most likely to be the path of the virus’s an initial arrival in Wuhan.

Lipkin states there is no proof that the virus entered the market through infected frozen wild animals. It could have simply as quickly been lugged in through infected human being who tackled wild animals, that says.

Was the virus turn in animals in China before the pandemic?

To establish which pet passed the virus to people, researchers require to uncover evidence the the virus in that species. Researchers in China tested some 30,000 wild, farmed and also domestic pets in 2019 and also 2020 but found no evidence of active or previous SARS-CoV-2 infection, other than in part cats in Wuhan in in march 20205.

However, Ben Embarek says these surveys were not representative of China’s overall animal population, and also that many much more animals should be tested for traces that infection, an especially on wildlife farms. “The lot of testing that’s been done is not sufficient to say, in any type of way, that wildlife farms were not transporting the virus,” claims Daszak.

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The explosive way in i m sorry the outbreak took turn off in Wuhan in December suggests that the virus was probably introduced once, through the wildlife trade, states Daszak. He states future testing should focus on farmed wild animals.