The incoming White House chief of staff, Rep. Mark Meadows of North Carolina, was among three Republican congressmen who said Monday that they were quarantining themselves because of suspected contact with a confirmed carrier of the novel coronavirus.

A spokesman, Ben Williamson, said Meadows learned this weekend he “may have come in contact” with the individual who attended the annual Conservative Political Action Conference in suburban Washington late last month. Meadows tested negative for the virus and is not displaying symptoms but is remaining home in self-quarantine until Wednesday, Williamson said in a statement.

Trump named Meadows his chief of staff on Friday evening, replacing Mick Mulvaney. Williamson’s statement did not address whether Meadows physically interacted with Trump since the conference last month.

Rep. Douglas A. Collins (R-Ga.) said March 9 he's quarantining himself after being near a coronavirus carrier in February, but on March 6 he was with Trump. (The Washington Post)

Two other lawmakers also said Monday they had contact with the same individual at CPAC — both of whom later interacted with the president.

Rep. Matt Gaetz (R-Fla.) rode with Trump on Air Force One as he flew from Florida to Washington on Monday. He said he had no symptoms but was awaiting the results of tests.

In an interview, Gaetz said he was put into a “closed-up room” on Air Force One after he found out about his exposure to the virus. After the plane landed, Trump “coaxed” him up front before leaving the aircraft. “He was not hyper-cautious about being in the same space that I was in,” Gaetz said. “I refused to go into his office; I stood outside the door. I told him he could talk from that distance.”

Rep. Douglas A. Collins (R-Ga.), who came in contact with the same carrier of the virus at CPAC, joined Trump during a visit Friday to the Georgia-based Centers for Disease Control and Prevention. Photos from that day show Collins shaking the president’s hand on the tarmac in Georgia.

“While I feel completely healthy and I am not experiencing any symptoms, I have decided to self-quarantine at my home for the remainder of the 14-day period out of an abundance of caution,” Collins said in a statement.

Concern over Capitol Hill’s vulnerability to a coronavirus outbreak exploded Monday as six lawmakers announced they were quarantining themselves because of contact with confirmed carriers. None of the six — members of both parties and both chambers — reported any symptoms of respiratory illness in their statements, but their proximity to confirmed cases highlighted the risks to Congress members and their aides as the coronavirus outbreak expands to pandemic proportions.

They travel frequently. They spend their days meeting people, shaking hands and giving hugs. Their workplace is visited by millions each year. And many, including their most senior leaders, are older — a significant risk factor in coronavirus deaths.

Five of the six — Gaetz, Collins, Sen. Ted Cruz (R-Tex.), Rep. Paul A. Gosar (R-Ariz.) and Meadows — attended the CPAC meeting, just one of many public gatherings where lawmakers, aides and other political players are in proximity with potential carriers of the virus.

The sixth lawmaker, Rep. Julia Brownley (D-Calif.), said Monday that she met with a person in Washington last week who has since tested positive for the virus and that she would be “working remotely” as a result. “Out of an abundance of absolute caution, my D.C. staff and I are self-monitoring and maintaining social distancing practices,” she said.

Gaetz and Brownley said they were closing their offices in Washington.

Gaetz attracted attention last week when he wore a gas mask on the House floor as Congress overwhelmingly approved an $8.3 billion aid package to deal with the virus.

A seventh lawmaker, Rep. Louie Gohmert (R-Tex.), said he possibly had been exposed to the carrier at CPAC, but after discussing his situation with a CDC physician, he decided to return to work.

The expanding coronavirus threat is forcing top congressional leaders to balance the need to go about the people’s legislative business and the risk of operating what could be a giant, ­marble-enclosed petri dish as the pathogen spreads.

Leaders of the House and Senate have taken a measured approach, consulting closely with the congressional attending physician and refraining from announcing substantial restrictions.

Sen. Richard J. Durbin (D-Ill.), the No. 2 Senate Democrat, said it was too early to consider cutting short legislative sessions or shutting down Capitol tours but said senators needed to consider significant changes to their usual routines to prevent an outbreak inside the legislature.

“Our lifestyle is the exact opposite of a quarantine. We’re by nature public animals and in contact with the public,” Durbin said, also noting the advanced age of many senators. “We’ve got to be sensible about this. Health is the most important thing for all of us. We don’t want to overreact, but let’s wait and see what happens.”

Durbin spoke on the phone later Monday with Anthony Fauci, the top federal official on infectious diseases, who advised the senator to query visitors to his office on whether anyone was sick and to station bottles of hand sanitizers before visitors can get beyond the front desk.

In a letter to House Democrats on Monday night, Speaker Nancy Pelosi (D-Calif.) said the caucus would hear from the sergeant at arms, the attending Capitol physician and the chief administrative office for an update on protocols Tuesday morning, but “at the present time, there is no reason for us not to continue with our vital legislative work in the Capitol.”

House Majority Leader Steny H. Hoyer (D-Md.) said leaders have been in discussions with the Capitol physician and other health experts, including CDC officials.

“At this point in time . . . we don’t have any advice that tells us that we ought to shut down, not have sessions, not have the Capitol open,” he said. “But we are very, very concerned.”

Hoyer added that members of Congress cannot legislate from their homes to address the crisis, “so to the extent that we can be here, we think that’s good policy.”

Members have already started making changes, whether by stepping up their hygienic precautions or canceling events.

Rep. Jimmy Panetta (D-Calif.) on Monday canceled town hall meetings he had scheduled in his Northern California district during next week’s planned congressional recess, citing the virus risk. He is substituting smaller roundtable events with health-care experts that he plans to publicize locally to circulate reliable medical guidance.

Panetta watched the changing practices play out in real time at another large gathering of politicians — a civil rights commemoration in Selma, Ala., this past weekend — as concerns about community transmission of the virus in the United States began to take hold.

“You know, when we got on the plane, it was handshakes, and by the end of it, people had started to get into that habit [of giving elbow taps] — nevertheless, it’s still difficult for people like me,” said Panetta, who greeted a reporter in the Capitol with a firm handshake.

Signs of caution have grown more common throughout the Capitol over the past week, from a proliferation of hand-sanitizer dispensers to the removal of communal snacks from some congressional offices. Pelosi (removed an open bowl of nuts from her conference room, leaving only individually wrapped Ghirardelli chocolates for visitors to sample.

House aides said there have been private discussions about whether the coming recess could be extended indefinitely. Congress must act by March 15 to extend some critical foreign surveillance authorities but has no other pressing deadlines until May 22, when authority for several key health-care programs will expire.

Lawmakers acted last week to pass $8.3 billion in emergency funding to address the coronavirus response, a measure that is expected to support the federal response for at least the coming weeks. But White House officials and some lawmakers are already discussing a possible economic aid package aimed at reassuring financial markets and staving off a possible recession.

Whether those negotiations will require all members of Congress and their staffs to be going about business as usual in Washington remains to be seen. Pelosi told reporters Thursday that she would continue to follow the guidance of medical experts but saw no immediate need to curtail access to the Capitol or the congressional schedule.

That was before news that congressional Republicans had been potentially exposed to the virus at CPAC — and that many more lawmakers and aides attended an even larger event, the American Israel Public Affairs Committee policy conference, where at least two coronavirus carriers were present but did not appear to directly interact with any congressional aides.

The congressional attending physician said in a statement Monday that the infected person who attended CPAC was able to provide public health officials with the names of people he had interacted with, including “several” members of Congress. Those lawmakers, the statement said, were contacted and interviewed and found to be at “low risk” for infection; some opted to engage in a self-quarantine out of an abundance of caution.

“The Office of Attending Physician supported this overall prudent individual choice by the members due to the unique requirements of members of Congress and their travel, professional work, and frequent interaction with members of the public,” the statement said.

Another consideration that some congressional aides have acknowledged is the increased risk that the coronavirus poses to older people. The average age of the House is 57.6 years, with 76 members 70 or older. For the Senate, the average is 62.9 years, with 27 age 70 or over.

Pelosi is 79 and Hoyer is 80, while Senate Majority Leader Mitch McConnell (R-Ky.) is 78 and Durbin is 75. Sen. Charles E. Grassley (R-Iowa), who as Senate president pro tempore is third in line to the presidency after Vice President Pence and Pelosi, is 86.

At a briefing Monday, Nancy Messonnier, the director of the National Center for Immunization and Respiratory Diseases at the CDC, indicated that people over 80 are at the greatest risk to the virus.

“I really think it’s important for the American public to understand the risk,” Messonnier said. “We use these broad categories of over 60 or over 65, but the data really says that as you get older the risk goes up.”

Rep. Barbara Lee (D-Calif.), 73, declined to directly address the age-related implications of the outbreak. She said that members are facing this just like the public at large, listening to health experts and following their leaders’ cues.

“We see a balance and take precaution and do everything that the public is doing in terms of the public health requirements here on Capitol Hill,” she said. “And I think everyone needs to know that no one is exempt from this.”

Paul Kane, Seung Min Kim and Ben Terris contributed to this report.

Correction: An earlier version of this report incorrectly said Panetta was at a Selma event on March 1. He was there this past weekend.