WASHINGTON — The government’s top infectious disease expert said on Tuesday that the rate of new coronavirus infections could more than double to 100,000 a day if current outbreaks were not contained, warning that the virus’s march across the South and the West “puts the entire country at risk.”
Dr. Anthony S. Fauci, the director of the National Institute of Allergy and Infectious Diseases, offered the grim prediction while testifying on Capitol Hill, telling senators that no region of the country is safe from the virus’s resurgence. The number of new cases in the United States has shot up by 80 percent in the past two weeks, according to a New York Times database, with new hot spots flaring far from the Sun Belt epicenters.
“I can’t make an accurate prediction, but it is going to be very disturbing, I will guarantee you that,” Dr. Fauci said, “because when you have an outbreak in one part of the country, even though in other parts of the country they are doing well, they are vulnerable.”
New flash points have weighed down talk of a resumption of normal life and a quick economic rebound. The chairman of the Federal Reserve, Jerome H. Powell, issued his own gloomy assessment, cautioning lawmakers on Tuesday of an “extraordinarily uncertain” moment facing the American economy.
“A full recovery is unlikely until people are confident that it is safe to re-engage in a broad range of activities,” Mr. Powell told a House committee, adding that a second wave “could force people to withdraw” and “undermine public confidence, which is what we need to get back to lots of kinds of economic activity that involve crowds.”
The twin hearings on Capitol Hill mirrored concerns roiling states where hospitalizations are rising, intensive care units are filling up and business establishments are again shutting their doors. Dr. Fauci particularly implored states to shut down indoor drinking establishments, declaring, “Congregation at a bar, inside, is bad news.”
And Dr. Robert Redfield, the director of the Centers for Disease Control and Prevention, admonished American Airlines for beginning to sell flights to their capacity, which would make onboard social distancing impossible.
“When they announced that the other day, obviously there was substantial disappointment,” Dr. Redfield said, adding, “We don’t think it’s the right message.”
Around the nation, and the world, it became painfully clear that, despite President Trump’s recent suggestion that the virus would “fade away,” the pandemic is getting worse.
More than 46,000 coronavirus cases were announced across the United States on Tuesday, the most of any day of the pandemic. Officials in eight states — Alaska, Arizona, California, Georgia, Idaho, Oklahoma, South Carolina and Texas — also announced single-day highs.
Case counts have climbed sharply in many of the states that were the first to reopen, including Florida and Texas, which recently forced bars to close again. In Texas, the bar closures spurred protests at the State Capitol and the governor’s mansion on Tuesday.
In Arizona, officials identified more than 4,600 new coronavirus infections on Tuesday, by far the state’s most in a single day. California’s case count has soared, surpassing 220,000 known infections.
Vice President Mike Pence, the administration’s point person on the virus, insisted that the situation was not dire, telling reporters in suburban Washington, “We’re in a much better place than four months ago, even two months ago.” Mr. Pence has said the new infections are primarily hitting younger people who get less sick.
The governors of New York, New Jersey and Connecticut — three former hot spots in the Northeast — were less sanguine, telling travelers coming into the region to quarantine for 14 days. New York added eight states — California, Georgia, Idaho, Iowa, Louisiana, Mississippi, Nevada and Tennessee — to a quarantine list that already included Alabama, Arkansas, Arizona, Florida, North Carolina, South Carolina, Texas and Utah. New Jersey and Connecticut are advising travelers from the 16 states to quarantine.
But in Florida, where more than 6,000 new cases were reported on Tuesday, Gov. Ron DeSantis, a Republican, remained defiant. On Friday, the state abruptly banned drinking in bars, though they can still sell food and alcohol for takeout. On Tuesday, Mr. DeSantis said at a news conference in Juno Beach that was enough: “We’re not going back, closing things.”
With the virus not under control in the United States, the European Union announced on Tuesday that it would open its borders to visitors from 15 countries — but not from America.
Even states that had reported improvements were starting to see the number of new cases rise, causing governors to rethink their plans to get residents back to work.
“We are now having 40-plus-thousand new cases a day. I would not be surprised if we go up to 100,000 a day if this does not turn around,” Dr. Fauci testified, adding, “I think it is important to tell you and the American public that I’m very concerned because it could get very bad.”
As to bars, he said, in his customary clipped fashion: “Outdoor better than indoor. Bars really not good. Really not good. Congregation in a bar inside is bad news. We’ve really got to stop that right now when you have areas that are surging like we see right now.”
Dr. Fauci and Dr. Redfield were among four top government doctors involved in the coronavirus response to testify on Tuesday; Adm. Brett P. Giroir, the assistant secretary for public health, and Dr. Stephen Hahn, the commissioner of food and drugs, also appeared. All four officials also appeared before House lawmakers last week, when Dr. Redfield warned of a potentially crippling second wave of the virus that would coincide with flu season — a warning he reiterated on Tuesday.
But beyond the spike in cases, they told lawmakers they had another pressing concern: Large swaths of the American population may refuse a coronavirus vaccine once one becomes available, which could seriously hamper efforts to control the pandemic and prevent the nation from turning the corner toward a full reopening.
Dr. Redfield told senators that his agency has spent about three months developing a plan to rebuild “vaccine confidence.” Senator Patty Murray of Washington, the top Democrat on the Health Committee, sounded alarmed, telling Dr. Redfield to speed up the work.
“We need to see that plan,” she said. “We need to know what it is. The public needs to know what it is.”
Dr. Redfield said that the C.D.C.’s plan was being developed with Operation Warp Speed, the Trump administration’s crash vaccine program that aims to have 300 million doses of a vaccine by early next year. Officials at the Defense Department and the Department of Health and Human Services involved in that project have spent significant time discussing a public-relations campaign that will in part try to win over Americans suspicious of a coronavirus vaccine, according to a senior administration official.
There are more than 140 vaccines being developed against the coronavirus. Seven in 10 Americans have said they would get vaccinated against the novel coronavirus if immunizations were free and available to everyone, according to recent polling — a number that health officials fear may not be enough to achieve “herd immunity,” a term that signifies that a vast majority of a population has protection against infection.
At least 70 percent will need to be immune to the virus to reach that point, according to researchers at Johns Hopkins University.
Officials are particularly concerned that African-Americans and others who have been hit hard by the pandemic may be hesitant about vaccinations because of longstanding suspicions of government programs like the Tuskegee experiment, in which poor Black men suffering from syphilis were left untreated and monitored.
“It is a reality: a lack of trust of authority, a lack of trust in government and a concern about vaccines in general,” Dr. Fauci said. He added that there needed to be “boots on the ground,” especially near minority communities that “have not always been treated fairly by the government.”
The official topic of Tuesday’s hearing was how to get children safely back to school, but there seemed to be no agreement on that, and no universal plan to do so. The American Academy of Pediatrics has come out strongly in favor of bringing children back to the classroom in the fall, saying in a statement that “schools are fundamental to child and adolescent development and well-being.”
Dr. Fauci agreed, but said each school district must make decisions based on the course of the pandemic in its area.
Masks — and Mr. Trump’s refusal to wear one — were a central issue at the hearing. The Republican chairman of the Health Committee, Senator Lamar Alexander of Tennessee, prefaced his opening statement with an appeal to the president to set a better example by occasionally covering his face.
Mr. Alexander lamented that masks had “become part of the political debate,” with people’s decision about whether to wear one dependent on their views of Mr. Trump.
“The president has plenty of admirers,” Mr. Alexander said. “They would follow his lead; it would help end this political debate. The stakes are too high for this political debate about pro-Trump, anti-Trump to continue.”
In his testimony before the House Energy and Commerce Committee last week, Dr. Fauci warned that the next two weeks would be critical to controlling the virus’s spread, and said it was not yet under control in the United States. On Tuesday he sounded even more downbeat, provoking a backlash from one Republican, Senator Rand Paul of Kentucky, who delivered a five-minute sermon denouncing “central planners” and health experts who opine on matters like sports.
“Dr. Fauci, every day, virtually every day, we seem to hear from you things we can’t do,” Mr. Paul, an ophthalmologist, said, adding: “All I hear is, we can’t do this. We can’t do that. We can’t play baseball.”
Dr. Fauci agreed that he was “completely unqualified to tell you whether you can play a sport or not,” but added that he was only trying, “to the best of my ability,” to disseminate facts and evidence about the outbreak.
The senator sounded exasperated. “We just need more optimism,” he said.
But Dr. Fauci stood firm. “We cannot forget,” he told senators at the end of the session, “that what was thought to be unimaginable turned out to be the reality that we’re facing right now.”
Patricia Mazzei contributed reporting from Miami.