WASHINGTON — The previous director of the Facilities for Illness Management and Prevention accused prime federal well being officers on Wednesday of excluding him from discussions in early 2020 about whether or not the coronavirus was the results of a laboratory leak — an assertion that one of many officers, Dr. Anthony S. Fauci, later stated had “nothing to do with actuality.”

Three years into the pandemic, the accusation by the previous C.D.C. director, Dr. Robert R. Redfield, put a highlight on the lingering bitterness and partisan divisions across the scientific query of the virus’s origins.

Dr. Redfield, a virologist who ran the C.D.C. throughout the Trump administration, believes the pandemic was most definitely the results of a lab leak. He testified on Wednesday on the first listening to of the Home Choose Subcommittee on the Coronavirus Pandemic, which is digging into the origins of a virus that has killed practically seven million individuals worldwide.

The listening to produced no new proof however loads of political theater, and it made clear simply how tough it could be to show up conclusive proof about whether or not the virus escaped from a lab or spilled over from animals to people naturally. It’s a query price answering, stated Consultant Ami Bera, Democrat of California, a health care provider who serves on the subcommittee and stated he was agnostic on the problem.

“Assigning blame will not be going to carry again seven million individuals,” Mr. Bera stated in an interview. “However it would possibly stop one other seven million deaths, if we perceive what occurred.”

Dr. Redfield stated the reply would in all probability come from intelligence businesses, not scientists, and lawmakers of each events appear to agree. Final week, the Senate handed a invoice that will order the declassification of intelligence associated to the Wuhan Institute of Virology, a laboratory that focuses on coronavirus analysis in Wuhan, China, the place the pandemic started. The Home is scheduled to take up the measure on Friday.

On the opposite facet of the Capitol advanced, the director of nationwide intelligence, Avril D. Haines, instructed the Senate Intelligence Committee on Wednesday that there was a consensus that the virus that causes Covid-19 was not engineered as a organic weapon, however that intelligence businesses disagreed on whether or not it leaked from a lab or got here from pure publicity to an contaminated animal. China has destroyed proof, complicating the seek for the trigger.

“We’ve been attempting to gather further info, and I feel you’re completely proper that China has not totally cooperated,” Ms. Haines stated, responding to a query from Senator Marco Rubio, Republican of Florida and the committee’s vice chairman. “And we do assume that’s a key essential hole that will assist us to grasp what precisely occurred.”

In the US, the notion that the coronavirus emerged from a lab was initially dismissed as a conspiracy principle by critics of President Donald J. Trump, who embraced the concept whereas attempting in charge China for the pandemic. However it’s now getting a re-assessment, partly as a result of new intelligence has led the Power Division to conclude, with low confidence, that the pandemic was most definitely the results of a lab accident.

“There isn’t a smoking gun proving a laboratory origin speculation, however the rising physique of circumstantial proof suggests a gun that’s at very least heat to the contact,” stated one other witness on the Home listening to, Jamie Metzl, a senior fellow on the Atlantic Council who labored within the Clinton administration and described himself as a Democrat.

In making the case for a laboratory leak, a number of witnesses centered on a selected function of the virus that causes Covid-19. That function, known as a furin cleavage website, helps the virus effectively infect human cells.

In 2018, EcoHealth Alliance, a analysis nonprofit, and a number of other of its companions, together with the Wuhan Institute of Virology, sought funding from the Protection Division to experiment on coronaviruses that would unfold in people. Their proposal, which was rejected, concerned learning furin cleavage websites.

One of many witnesses, Nicholas Wade, who served as The New York Occasions’s science editor within the Nineteen Nineties and left the information group on the finish of 2011, instructed lawmakers that researchers could have already carried out experiments through which they inserted furin websites into coronaviruses.

Mr. Wade questioned the chance that evolution would “produce, at that very time and at that very place, a virus of the precise kind described” within the teams’ proposal.

EcoHealth stated on Wednesday that researchers didn’t do the experiments earlier than proposing them partly as a result of they “required a considerable funds.”

No proof has but emerged displaying that the Wuhan lab’s researchers had any virus in its collections that would have been altered to make the virus that causes Covid-19. Scientists have stated pure evolutionary processes might simply clarify the presence of the furin cleavage website.

Whereas shut recognized relations of the coronavirus that emerged in Wuhan are lacking a furin cleavage website, many different coronaviruses have that very same signature function, together with coronaviruses that trigger colds.

Dr. Redfield testified that he was alarmed by the furin cleavage website, which, he stated, “completely adjustments the orientation now so it has excessive affinity for human receptors,” reworking its capacity to bind to human cells.

However coronaviruses, together with bat coronaviruses found in Laos in 2020, can latch onto human cells with out a furin cleavage website. Stephen Goldstein, a virologist on the College of Utah, stated the furin website affected the virus’s route of entry into cells, however not its binding capacity.

“Every part he stated was mistaken,” Dr. Goldstein stated of Dr. Redfield. “Robert Redfield is both ignorant or mendacity to Congress.”

Dr. Redfield’s accusation that he was excluded from discussions over the virus’s origins revolves round e mail exchanges and a telephone dialog in early February 2020 — a month earlier than the World Well being Group declared a pandemic — within the rush to determine the place the brand new virus had come from.

On the time, some scientists stated the furin cleavage website made them ponder whether the virus had been engineered. The emails present that Dr. Jeremy Farrar, a British medical researcher, arrange a name so scientists might focus on it. Dr. Fauci, on the time the director of the Nationwide Institute of Allergy and Infectious Ailments, and Dr. Francis S. Collins, who led the Nationwide Institutes of Well being, have been on the decision.

Dr. Redfield stated he didn’t discover out in regards to the name till a lot later, when the emails grew to become public. The messages don’t consult with or title Dr. Redfield. However he instructed lawmakers that when he realized of them, he concluded that Dr. Fauci and Dr. Collins had deliberately excluded him as a result of he believed the virus had originated in a lab.

“It was instructed to me that they wished a single narrative and that I clearly had a unique standpoint,” Dr. Redfield stated. He didn’t specify who made that comment, and he declined to reply questions after the listening to.

However in an interview, Dr. Fauci stated he and Dr. Collins didn’t arrange the decision, which introduced collectively evolutionary biologists, together with some who suspected that the virus had been made in a lab. He additionally stated he didn’t know what Dr. Redfield’s views have been on the time.

“It doesn’t make any sense that he was excluded as a result of he had a unique opinion,” Dr. Fauci stated. “Half the individuals on the decision felt that approach.”

A number of days after that decision, the scientists who had suspected a lab leak modified their assessments, as they’d initially stated would possibly occur. After doing additional investigation, they concluded that the genetic proof was inconsistent with a virus that had been intentionally engineered, and so they later printed a research laying out their analysis.

If there was a single level of settlement at Wednesday’s listening to, it was that politicians ought to put partisanship apart in order that an unbiased inquiry might proceed. However lawmakers didn’t at all times follow what they preached.

Democrats used a few of their time to assault Mr. Trump and assail Mr. Wade, who wrote a 2014 ebook, “A Troublesome Inheritance,” that argued there’s a organic foundation for race. Consultant Raul Ruiz of California, the subcommittee’s prime Democrat, known as Mr. Wade’s concepts “discredited, unscientific and dangerous.” Mr. Wade countered that his ebook was “explicitly antiracist,” including, “I stress the truth that we’re all variations on the identical human genome.”

Republicans, in flip, repeatedly attacked Dr. Fauci, who has change into a frequent goal for the get together. That prompted a warning from Mr. Metzl, who cautioned lawmakers towards specializing in Dr. Fauci as they seek for the pandemic’s origins.

“If we make it primarily about Dr. Fauci,” he stated, “we might be inappropriately serving the Chinese language authorities a propaganda coup on a silver platter.”

Julian E. Barnes contributed reporting.