There is a "zero percent" chance that the novel coronavirus that caused the COVID-19 pandemic was leaked from a laboratory of the Wuhan Institute of Virology (WIV), French biosecurity expert Gabriel Gras refuted the lab leak theory during an interview with Xinhua.

Gras was employed as a technical expert at the French embassy in China for the implementation of the French-Chinese cooperation on emerging infectious diseases between 2012 and 2017, during which period he visited the lab once or twice a month.

The biosafety level 4 (BSL-4) laboratory was constructed in close cooperation between France and China, said Gras. As the one who supervised its construction and accreditation, Gras said he had "no doubt" about the lab's safety. "The theory that the virus escaped from Wuhan BSL-4 lab is not credible."

He noted that the lab was built and operated at a very strict standard. With a background as a biosecurity specialist and virologist, Gras said he was completely involved in verifying that in his daily work.

Gras explained that operating a BSL-4 lab is very expensive, both in terms of money and time. Coronaviruses, including the novel coronavirus, belong to BSL-3 or BSL-2 pathogens, rather than BSL-4 ones, and it is common sense that people will not use a BSL-4 facility to study BSL-3 pathogens or a BSL-3 facility to BSL-2 pathogens.

"Using a BSL-4 lab to work with a coronavirus is like using a 20-tonne crane to move a 30-kg refrigerator, which would be completely illogical," said the expert.

Since there is no reason to culture the novel coronavirus in the BSL-4 lab, there is no possibility of a lab leak, he added. He said the current scientific consensus is that the novel coronavirus originated in the wild, not in the lab when responding to the lab-made hypothesis.

When a virus is found, it's either in samples taken in the wild or in samples taken from patients, said Gras, adding that published evidence is opposite to the theory that the novel coronavirus present in the lab before the start of the pandemic.

Gras remained the same stance as in an interview with South China Morning Post in June when he said the discussion about the origin had become politicized. "For me, this is [no longer] a scientific issue."