The claim that the SARS-CoV-2 leaked from a Wuhan lab goes against science, a senior official of the National Health Commission (NHC) said Thursday.

Zeng Yixin, vice director of the NHC, said he was surprised to hear that some people have claimed the SARS-CoV-2, the virus that causes COVID-19, escaped from the Wuhan Institute of Virology (WIV).

The claim is disrespectful to common sense, and goes against science, Zeng told a press conference on the coronavirus origin-tracing work, which is held by China's State Council Information Office.

Yuan Zhiming, director of the National Biosafety Laboratory at the WIV, said that his lab, which studies class four pathogens and boasts the highest biosafety rating, has not had any incidents of leakage since it was put into operation in 2018.

Zeng added that some claims, such as so-called infection of three WIV staff, or the gain-of-function experiment on the novel coronavirus by the lab, are just rumors that have already been quashed.

He noted that it is widely accepted by genetic engineers that the artificial modification of a virus will definitely leave traces. Novel coronavirus has no such trace, which totally rules out the theory that it was man-made.

Up to now, none of the WIV staff members have been infected by the novel coronavirus, the lab has not carried out the gain-of-function experiment on the pathogen, and there is no so-called artificial novel coronavirus in the WIV, he reiterated.

World Health Organization (WHO) experts said after visiting the WIV that it was "extremely unlikely" that the virus spread from a lab leak, Zeng added.