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WHO says virus 'lab leak theory' needs more study

After two years of discounting a controversial pandemic theory, WHO released a report urging "further investigations into this and all other possible pathways."

WHO scientists arriving in Wuhan, China in January 2021
WHO scientists arriving in Wuhan, China in January 2021 (AN/CGTN)

GENEVA (AN) — After two years of mostly discounting the so-called lab leak theory of how the pandemic began, the World Health Organization released an eagerly awaited report recommending "further investigations into this and all other possible pathways."

A scientific advisory panel's 44-page preliminary report marks a distinct shift from an assessment last year by a WHO-led team of experts that the lab leak hypothesis — initially labeled a conspiracy theory — was "extremely unlikely," though the panel finds the strongest evidence still points to an outbreak caused by zoonotic transmission: an infectious disease transmitted between species from animals to humans, or vice versa.

Most of the panel's 27 experts say they agree "it remains important to consider all reasonable scientific data that is available either through published or other official sources to evaluate the possibility of the introduction of [the virus] into the human population through a laboratory incident." A footnote in the report says three members — from Brazil, China and Russia — did not agree with more examination of a possible lab leak because "there is no new scientific evidence to question the conclusion" of a WHO-convened global study published in March 2021.

With the emergence of the coronavirus, its origin story became, as with some other new pathogens, fodder for what many news media outlets dismissed as a conspiracy theory. Most prominent was the notion it was engineered in China's Wuhan Institute of Virology and escaped across the Yangtze River to the nearby Huanan Seafood Market, a so-called "wet market" that sells frozen seafood, live domesticated wildlife such as rabbits and bamboo rats, and other food, and is where many of the first COVID-19 cases were found.

Former U.S. President Donald Trump heavily promoted that theory without providing any evidence and, pointing to WHO's initial public praise of the Chinese government's handling of the coronavirus outbreak, accused the U.N. health agency of taking part in a Chinese coverup of the pandemic's origin. The charges further inflamed U.S.-China tensions, and more suspicion was raised by China's denials that the massive market in Wuhan sold live wild animals.

China's Foreign Ministry spokesperson Zhao Lijian told a regular press briefing in Beijing on Friday that "the lab leak theory is a false claim concocted by anti-China forces for political purposes. It has nothing to do with science." And, resurrecting Chinese propaganda that the U.S. Army may have started the pandemic as part of its research, he suggested the WHO panel "target highly suspicious laboratories such as those at Fort Detrick and the University of North Carolina."

"We always support and participate in science-based global origins-tracing. At the same time, we firmly oppose all forms of political manipulation," he said.

The panel notes, however, no new raw data is available from China to judge if the lab was a pathway for the virus. It says it believes more examination of this and other potential pathways is warranted and that it "will remain open to any and all scientific evidence that becomes available in the future to allow for comprehensive testing of all reasonable hypotheses."

'Gaps in our knowledge'

In keeping with WHO's previous analysis — that the initial spread of the coronavirus was likely transmitted from bats to humans through another animal and not from an accident in a Chinese lab — the panel says the epidemiological and sequencing data suggests the virus has "a zoonotic origin with the closest genetically related viruses being betacoronaviruses, identified in Rhinolophus bats in China in 2013 (96.1%) and Laos in 2020 (96.8%)."

The panel says it was given Chinese data involving unpublished blood samples from more than 40,000 people in Wuhan in 2019 that were tested for COVID-19 antibodies, but since none were found it did not appear that the virus was spreading widely before it was first detected at the start of 2020.

There is still a need to examine environmental samples collected from specific stalls and drains at the wet market in January 2020 that tested positive for COVID-19 "in areas known to have sold live animals," the panel says, and to do more studies into "possible animal sources from which the environmental contamination could have originated from have not been completed."

"Early investigations suggested that the Huanan Seafood Market in Wuhan played an important role early in the amplification of the pandemic with several of the patients first detected in December 2019 having had a link to the market and environmental samples from the market testing positive," the panel says. "There are, however, further studies needed to follow up on several gaps in our knowledge. For example, the source of [coronavirus] and its introduction into the market is unclear and it is yet to be determined where the initial spillover event(s) occurred."

The WHO panel, formally known as the Scientific Advisory Group for the Origins of Novel Pathogens (SAGO), has experts from 27 nations, including China and the U.S. Its job is to review  existing research, not to carry out its own investigation, and to advise WHO's senior officials. The panel's report notes that WHO Director-General Tedros Adhanom Ghebreyesus sent letters in February to China's Premier Li Keqiang and Health Minister Ma Xiaowei asking for additional data including information on the “laboratory hypotheses.”

Last year a WHO-led team of international and Chinese scientists provided more details about how COVID-19 was first reported in late 2019 in Wuhan, China, but it did little to advance what is already publicly known about the origins of the virus or to dispel skepticism among some officials in the United States and other nations about China's level of cooperation with WHO scientists.

It found an early outbreak may have occurred at the wet market but the virus did not necessarily originate there. The team told a press briefing in Wuhan, China, that it could not conclude whether the virus jumped directly from an animal to humans, or through an intermediary host such as a bamboo rat or pangolin, but it was "extremely unlikely" to have spread from a lab leak.

Usually, scientists take years to determine the source of a disease traced to animals. Another part of the reason the WHO panel did not count out the lab leak theory is there have been previous virus outbreaks caused by lab accidents. The virus that causes foot-and-mouth disease, for instance, was accidentally released from European labs on several occasions going back to 1960, causing public disease outbreaks. Smallpox outbreaks in 1966 and 1978 in the U.K. and a Marburg virus outbreak in Germany in 1967 were traced to labs.