WASHINGTON, United States (AFP) — Former US government scientist Anthony Fauci angrily denied covering up the origins of Covid-19 Monday in his first public congressional testimony since retiring as the face of the fight against the pandemic.

Fauci became the nation’s most trusted expert in the chaotic early days of the 2020 outbreak, but his clashes with former president Donald Trump over the response sparked fury on the right, and he now lives with security protection following death threats against his family.

Republicans accuse the 83-year-old immunologist of helping to set off the worst pandemic in a century by approving funding passed on to Chinese scientists they accuse of manufacturing the SARS-CoV-2 coronavirus that causes Covid-19.

He was pressed by Republicans on the House Select Subcommittee on the Coronavirus Pandemic on his knowledge of “gain of function” research, which seeks to enhance viruses as a way of finding ways to combat them.

The controversial technique is at the center of a theory that the pandemic originated in a lab leak.

But Fauci said it would be “molecularly impossible” for the bat viruses studied at the Wuhan Institute of Virology to be turned into the virus that caused the pandemic.

And he dismissed as “absolutely false and simply preposterous” Republican claims that he influenced the CIA’s analysis of whether the pandemic started naturally or escaped from the lab.

The director of the National Institute of Allergy and Infectious Diseases (NIAID) for 38 years until he stepped down in December 2022, Fauci helped craft federal policy during an outbreak that killed 1.1 million Americans.

His regular TV appearances correcting Trump’s misinformation about the pandemic earned him enemies among allies of the billionaire, who is bidding for a second term in November.

The panel has taken more than 100 hours of testimony and sifted through a mountain of documents in a 15-month investigation but has failed to turn up any evidence linking Fauci to potentially dangerous research in Wuhan.

The World Health Organization and scientists across the world have investigated the origins of the virus, most believing it to have spread from animals to humans in China.

A US intelligence analysis released last year said it was also possible that the virus was genetically engineered and escaped from the Wuhan lab.

Fauci told lawmakers it was “not a conspiracy theory” to discuss the merits of the lab leak theory.”What is a conspiracy theory is the kind of distortions of that particular subject, like, it was a lab leak and I was

parachuted into the CIA like Jason Bourne and told the CIA that they should really not be talking about a lab leak,” he said.