WASHINGTON — Home Republicans on Wednesday will dig into the origins of the coronavirus pandemic in a listening to that guarantees to be stuffed with political theater alongside substantive questions on laboratory security and what, if something, may have been finished to forestall the worst public well being disaster in a century.

The listening to of the Choose Subcommittee on the Coronavirus Pandemic is predicted to focus largely on the intensifying debate over whether or not Covid-19 was the results of a laboratory leak. Upfront of the session, Republicans issued a memorandum essential of Dr. Anthony S. Fauci, the previous director of the Nationwide Institute of Allergy and Infectious Illnesses and a frontrunner within the federal response to the pandemic.

Republicans have invited three witnesses: Dr. Robert R. Redfield, who served because the director of the Facilities for Illness Management and Prevention beneath President Donald J. Trump; Jamie Metzl, a senior fellow on the Atlantic Council; and Nicholas Wade, who served as science editor for The New York Instances within the Nineteen Nineties and left the information group on the finish of 2011. All have mentioned the virus could have by chance escaped from a laboratory.

Though the lab leak idea has acquired assist from a minority of American intelligence businesses, it lately gained a lift after new intelligence led the Power Division to conclude, albeit with low confidence, that the pandemic was most probably attributable to a laboratory accident.

The F.B.I. additionally believes that the reason for the pandemic was “most probably a possible lab incident,” the bureau’s director, Christopher A. Wray, confirmed final week. However 4 different intelligence businesses, in addition to the Nationwide Intelligence Council, have concluded, additionally with low confidence, that the virus most probably originated in animals after which unfold naturally to people. The C.I.A. has not taken a place.

Individually on Wednesday, senior intelligence officers are anticipated to replace senators about their ongoing investigation into the reason for the pandemic, as a part of an annual listening to on worldwide threats to nationwide safety. Avril D. Haines, the director of nationwide intelligence, will in all probability face questions concerning the various positions intelligence businesses have taken on the problem.

As a result of China has withheld proof, scientists could by no means resolve what brought on the pandemic, mentioned Senator Angus King, unbiased of Maine and a member of the Intelligence Committee.

“The extra essential query is, was this in some way purposeful,” Mr. King mentioned. He added, “If it was a leak from a lab, it tells you one thing, nevertheless it doesn’t inform you if it was in some way malicious.”

The coronavirus subcommittee within the Home is made up of 9 Republicans and 7 Democrats. Its members embody Consultant Marjorie Taylor Greene, the Georgia Republican recognized for her embrace of conspiracy theories, and Consultant Ronny Jackson, Republican of Texas, the previous White Home physician who made headlines for his rosy evaluation of Mr. Trump’s well being. The Pentagon’s inspector normal later discovered that he drank on the job and bullied his workers.

The chairman of the subcommittee, Consultant Brad Wenstrup, Republican of Ohio, and its prime Democrat, Consultant Raul Ruiz of California, have labored collectively on laws up to now. Mr. Wenstrup, a podiatrist, and Mr. Ruiz, an emergency doctor, have each mentioned they want to rise above partisan politics and conduct an intensive inquiry into the pandemic’s origins.

“This investigation should start with the place and the way this virus took place in order that we are able to try to ‘predict, put together, defend, or forestall’ it from occurring once more,” Mr. Wenstrup mentioned in an announcement.

However the political dynamics, notably across the function of Dr. Fauci, could make that unattainable. Lengthy earlier than they took over the Home, Republicans vowed that they might examine him in the event that they gained management of the chamber.

Ms. Greene has gone as far as to name him an “enemy to the world.”

The divisive debate over the lab leak idea facilities largely round analysis performed on the Wuhan Institute of Virology, a Chinese language laboratory that research coronaviruses within the metropolis the place the pandemic started.

Dr. Fauci isn’t on the witness record for Wednesday’s listening to; in a short interview, he mentioned he was not requested to testify. However on Sunday, Republicans on the subcommittee launched a memorandum asserting that he had inappropriately pushed for publication of a scientific paper to tamp down the lab leak speculation — an accusation he known as “false and deceptive” in an announcement.

“I’ve acknowledged repeatedly that we should hold an open thoughts as to the origins of the virus, and that the origin of the virus must be the topic of ongoing, thorough and open-minded scientific research that follows the information and proof wherever it leads,” Dr. Fauci mentioned within the assertion. “That is still my aim at this time.”

Dr. Fauci has mentioned he believes the preponderance of the proof reveals that the pandemic originated in nature, though he stays open to the thought of a laboratory leak. The Republican memo spotlighted his actions in early February 2020 — greater than a month earlier than Covid-19 was declared a pandemic — and zeroed in on a collection of electronic mail exchanges amongst scientists and well being officers as they raced to evaluate the likeliest origin of the virus.

Amongst these included within the electronic mail exchanges have been Dr. Fauci; Dr. Francis S. Collins, then the director of the Nationwide Institutes of Well being; Kristian Andersen, a virologist on the Scripps Analysis Institute in California; and Dr. Jeremy Farrar, a British medical researcher who was then the director of the Wellcome Belief, a charitable group targeted on well being analysis. In December, the World Well being Group introduced that Dr. Farrar had been chosen as its new chief scientist.

In a single electronic mail that has garnered consideration because it was launched in 2021, Dr. Andersen wrote that sure options of the virus made him wonder if it had been engineered in a laboratory. After discussions with different scientists, he mentioned that they had discovered “the genome inconsistent with expectations from evolutionary idea.”

“However,” he added, “now we have to take a look at this rather more carefully and there are nonetheless additional analyses to be finished, so these opinions may nonetheless change.”

Inside just a few days, their evaluation had certainly modified. The staff of scientists investigating the origins wrote in a abstract of their findings that the genetic proof was inconsistent with a virus that had been intentionally engineered; in different phrases, they have been assured that researchers had not deliberately manufactured it.

In March 2020, Dr. Andersen and a number of other co-authors printed a research within the scientific journal Nature Drugs that described these findings. The research, titled “The Proximal Origin of SARS-CoV-2,” mentioned their analyses confirmed that the virus was “not a laboratory assemble or a purposefully manipulated virus.”

The research additionally mentioned that given the overlap that the authors had discovered between the coronavirus and associated viruses in nature, they “don’t imagine that any sort of laboratory-based state of affairs is believable.”

Republicans have urged that Dr. Fauci influenced the scientists’ change of coronary heart and pushed for publication of the proximal origin research in an effort to tamp down the thought of a lab leak — an assertion that each Dr. Fauci and Dr. Andersen have repeatedly denied.

Dr. Andersen and different scientists concerned within the research have mentioned that their views modified after just a few days of intense work. Emails which have since been made public point out that they consulted with virologists who had extra expertise finding out coronaviruses and who mentioned that the options which will initially have appeared worrisome didn’t the truth is recommend that the virus had been concocted in a lab.

A few of these options of the virus have been additionally recognized in associated coronaviruses in different species, strengthening the view that the options weren’t essentially lab-made.

Dr. Andersen mentioned that the Republican memo represented a flip away from scientific discussions of the virus’s origins. “I discover it deeply problematic how distant from the science now we have gotten in our effort to extra absolutely perceive the origin of the pandemic,” he mentioned.

The Republican memo claimed that the subcommittee had proof that Dr. Fauci had swayed the research, citing an electronic mail from Dr. Andersen to the scientific journal Nature that mentioned Dr. Fauci, amongst others, had “prompted” their effort “to offer agnostic and scientifically knowledgeable speculation across the origins of the virus.”

Dr. Fauci mentioned within the assertion that he didn’t immediate the drafting of any article meant to rule out a laboratory leak and was not concerned in drafting or modifying of any portion of the printed research. “My solely aim,” he wrote, “was to encourage the knowledgeable virologists to judge the origin of the Covid-19 virus by offering an goal and scientifically sound examination of the data accessible on the time.”

How a lot consideration the Republicans’ memo will garner at Wednesday’s listening to is unclear. Not one of the witnesses invited by Republicans have been concerned within the electronic mail exchanges in query.

Democrats on the subcommittee have invited Dr. Paul G. Auwaerter, the scientific director of the infectious ailments division on the Johns Hopkins College College of Drugs, to testify as nicely.

In an announcement, Mr. Ruiz, the highest Democrat on the panel, known as on Republicans to keep away from “politicization, excessive partisan rhetoric and conspiratorial accusations that vilify our nation’s public well being specialists,” and he urged them to let “the science and details prepared the ground.”

Julian E. Barnes contributed reporting.