The weekend release of the US Central Intelligence Agency (CIA) report favouring a laboratory leak as the likely origin of COVID-19 – albeit with “low confidence” – has reignited a vitriolic debate.

On the one side of the divide are those who argue that SARS-CoV2, the virus causing COVID-19, originated from a lab leak from the Wuhan Institute of Virology (WIV) that was studying coronaviruses in bats.

Some researchers who favour the lab-leak thesis argue that the virus contains unusual features that indicate it may have been genetically modified by humans. These focus on the virus’s furin cleavage site, a strange feature on the spike protein of the virus that is not present in other coronaviruses, that cast doubt on whether the virus had evolved naturally.

The other camp (the zoonosis thesis) believes the virus was transmitted from bats to humans via an animal source – Animal X – that has never been conclusively identified but is believed to have been in the Huanan wet market in Wuhan.

They argue that early COVID-19 cases centred around the market and environmental swabs that tested positive for SARS-CoV-2 clustered in the corner of the market where animals were sold.  SARS-CoV2 is not the same as the coronavirus in bats, although there is one that is 96% similar. It would have needed to have mutated in “Animal X” in order to infect humans.

Virus origins team

The World Health Organization (WHO) assembled a team of independent scientists to examine the origin of the pandemic in 2020, but the Chinese government denied it access to the data it requested on a visit to Wuhan in January 2021.

The origins team report in March 2021 posed four possible hypotheses about the virus’ origin, but concluded that zoonotic transmission was the most plausible, describing a lab leak as “extremely unlikely”.

But the failure of the WHO-convened team to carefully consider the possibility that a biosafety accident caused the pandemic was heavily criticised by a group of international experts, in a series of open letters to WHO. 

WHO Director-General Dr Tedros Adhanom Ghebreyesus said candidly in July 2021 that China’s failure to share data meant that a lab accident could not be ruled out.

“There was a premature push to refute one of the [origins] options, the laboratory theory. I was a lab technician myself, an immunologist, and have worked in the lab and lab accidents happen,” said Tedros during a WHO media briefing in July 2021.

China rebuffs scientific advisory group 

The WHO then established an international Scientific Advisory Group on Origins of Novel Pathogens (SAGO) to replace the group that led the first mission to Wuhan. 

However, China refused SAGO’s request in July 2021 to review more data on Wuhan’s sensitive coronavirus research laboratories, and the wild animal species on sale in 2019 at the city’s live animal markets. (China favoured the thesis that the virus came from imported frozen goods).

“We will not accept such an origin-tracing plan as it, in some aspects, disregards common sense and defies science,” said Zeng Yixin, Vice Minister of the National Health Commission.

“We hope the WHO would seriously review the considerations and suggestions made by Chinese experts and truly treat the origin tracing of the COVID-19 virus as a scientific matter, and get rid of political interference,” Zeng said.  

The CIA’s report, initiated during the Biden Administration but released by Donald Trump’s pick for CIA head, John Ratcliffe, was not the result of any new evidence but rather a re-examination of available evidence, according to reports.

However, the CIA added that it  “continues to assess that both research-related and natural origin scenarios of the Covid-19 pandemic remain plausible”.

In 2023, the US Federal Bureau of Investigation (FBI) said it favoured the lab leak theory as did a US Congress sub-committee in December 2024. 

‘Gain of function’ research?

Some of those who favour the lab leak thesis have claimed that there was a cover-up of the lab leak theory because a US research group, EcoHealth Alliance, had been involved with the WIV and received government research funds.

They allege that the WIV, assisted by EcoHealth, engaged in “gain of function” research that involved manipulating coronaviruses to see how they responded to environmental pressures.

A 2018 grant application submitted by EcoHealth to the US Defense Advanced Research Projects Agency (DARPA) shows the group wanted to conduct gain-of-function research that included inserting novel cleavage sites into coronaviruses in their lab. This was denied as it was deemed it too risky.

China rejects CIA report

Over the weekend, Chinese authorities dismissed the CIA report as being unhelpful and motivated by politics. On Saturday, a spokesperson for China’s US embassy said the CIA report has no credibility.

“We firmly oppose the politicisation and stigmatisation of the source of the virus, and once again call on everyone to respect science and stay away from conspiracy theories,” a spokesperson from China’s US embassy, Liu Pengyu, told Associated Press.

The failure of the Chinese government to allow independent scientists access to Wuhan, COVID-19’s “ground zero”, and various data sets, means that conclusive evidence to support one or other thesis is unlikely.

However, the politicisation of the quest to find the origins of SARS CoV2 has also polarised research and contaminated research.

Image Credits: CNN, CGTN, WHO.