Security personnel gather near the entrance of the Wuhan Institute of Virology during a visit by the World Health Organization team in Wuhan, China. Photo / AP
Republicans in the US Congress want to subpoena Peter Daszak, a British-born scientist, as part of an investigation in which they have concluded Covid-19 leaked from the Wuhan laboratory.
A report released by Republicans on the foreign affairs committee said the "preponderance of evidence proves" the virus leaked from the Chinese research facility "sometime before September 12, 2019".
It cited "ample evidence" that Wuhan Institute of Virology researchers - aided by US experts - were working to modify coronaviruses to infect humans.
The report foreshadows an August 24 deadline for a US intelligence review, ordered by President Joe Biden, into the causes of the pandemic. It is believed US intelligence officials have yet to reach a conclusion on whether the virus escaped from the lab, or passed from animal to human in a nearby market.
Michael McCaul, the leading Republican on the committee, accused China of "the greatest cover-up of all time".
In a statement accompanying the report he said Wuhan scientists should be sanctioned and that Daszak should be subpoenaed to answer "many questions" before the committee.
In June, Daszak recused himself from an inquiry into the origins of the pandemic amid concern over his links to the Wuhan lab. He was also a member of the WHO investigation into the source of the pandemic.
In February 2020 he co-authored a letter to The Lancet which "strongly condemned conspiracy theories suggesting that Covid-19 does not have a natural origin".
Daszak worked closely with Shi Zhengli, the Wuhan virologist nicknamed "Bat Woman" for her work on viruses in bats, and his US-based non-profit organisation had directed funding to Wuhan for virus research.
China denies the Wuhan lab leak theory facility and a team of international scientists last month published a review suggesting there's still scant evidence to support the theory.
The Republican report referred to under-reported information about lab safety protocols.
It detailed a request in July 2019 for an overhaul of a hazardous waste treatment system, which was less than two years old. That request included maintenance on an "environmental air disinfection system".
It raised questions about how well such systems were working in the months leading up to the outbreak, the report said, ading that: "Such a significant renovation so soon after the facility began operation appears unusual."
According to the report, satellite data in October 2019 showed a jump in visits to hospitals in Wuhan, along with a rise in people searching the internet for symptoms that could be linked to the virus.
It suggested the virus spread through Wuhan shortly before the Military World Games was held there in October 2019. That event became an "international vector spreading the virus to multiple continents around the world" as athletes returned home.