Dr Fauci told CNN on Thursday it was "nonsense" to infer from the email any cosy relationship between himself and the figures behind the Wuhan lab research.
Last week, the Chinese Foreign Ministry accused the United States of failing to be interested in "serious scientific tracing" of COVID-19's origins after President Joe Biden pledged to push Beijing to take part in a full-blown worldwide investigation into where the virus came from.
While Fauci has said that the U.S. "But we need to keep on investigating until a possibility is proven".
Last week, Fauci testified before Congress that there was no way to know if Chinese scientists at the Wuhan Institute of Virology lied and conducted those experiments on bat coronaviruses using USA tax dollars.
At a regular Friday briefing, he referred to a March 23 statement from the Wuhan Institute of Virology, stating that staff and graduates had not been confirmed to be infected with the virus.
US National Institutes of Health Director Francis Collins has denied ever rejecting the theory that the COVID-19 pandemic originated in China's Wuhan laboratory, but insisted that animal-to-human transmission was the most plausible explanation for the outbreak.
"Many thanks for your kind note", Dr Fauci replied.
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The interview was preceded by Chinese Foreign Ministry spokesperson Zhao Lijian claiming last week that the White House "doesn't care about [the] facts and truth" pertaining to the origins of the COVID-19.
Zhao called on the USA to open itself up to investigations into its own biological laboratories, including those located at the Naval Medical Research Centre's Biological Defence Research Directorate at Fort Detrick in Maryland, which is "full of suspicions". But this Peter Daszak, who is buddies with Fauci, who is thanking him privately in emails for covering up the Wuhan leak, ' Paul charged.
The origin of the virus is hotly contested, with US intelligence agencies still examining reports that researchers at a Chinese virology laboratory in Wuhan were seriously ill in 2019 a month before the first COVID-19 cases were reported.
The Kentucky Republican also said Daszak can not be part of any investigation into COVID-19 origins.
'Or any of these people who are in this close group of friends because they have an incentive to cover it up because they were funding the lab, ' Paul said. The copper mine they were working at in the mountains of the district of Tongguan in China's southwestern province of Yunnan and the bats that inhabit it are now a focal point of lab leak theory. 'Let me say clearly that as far as World Health Organization is concerned all hypotheses remain on the table'.
Paul also claimed that some of Fauci's emails showed that he was "very troubled" about some gain-of-function research being done - though it was not immediately obvious which emails the Kentucky Republican was speaking of.
"I'm stunned that Fauci would now ask this question", said Asher, who is now at the Hudson Institute, a conservative Washington-based think-tank.