Staggered by the resurgent novel coronavirus, cities and states are reinstituting restrictions on bars, pools and large gatherings days ahead of July 4 celebrations as the top U.S. infectious-disease expert warned Tuesday that the pandemic is out of control in some places and soon could reach 100,000 cases a day.

Nationally, new infections have topped 40,000 in four of the past five days during an accelerating outbreak that exceeds the worst days of April.

The number of people hospitalized with covid-19, the disease the virus causes, is surging in seven states, according to data tracked by The Washington Post. In Texas, Arizona, Nevada, South Carolina, West Virginia, Georgia and California, seven-day averages are up at least 25 percent from last week.

“I’m not satisfied with what’s going on because we’re going in the wrong direction,” Anthony S. Fauci said during a Senate hearing Tuesday.

Fauci, the director of the National Institute of Allergy and Infectious Diseases, said he would not be surprised to see the number of new infections more than double, from over 40,000 a day now to 100,000 a day. “We’ve really got to do something about that, and we need to do it quickly,” Fauci said under questioning from Sen. Elizabeth Warren (D-Mass.). “Clearly, we are not in total control right now.”

Fauci said half of all new cases are being recorded in just four states. Three of them — Arizona, Texas and Florida — are led by Republican governors who moved quickly, after being urged by President Trump, to reopen their economies but have since begun closing bars and beaches.

In Florida, where cases have spiked, Miami Mayor Francis Suarez, who last week ordered people in the city to wear masks in public amid a spike in cases, said a statewide policy should be a “no-brainer.” The mayor of Miami Beach also issued a penalty-bearing rule that requires that city’s residents to wear masks.

In the fourth state with a big increase in coronavirus cases, California Gov. Gavin Newsom, a Democrat, has taken a more cautious approach, imposing the country’s first statewide stay-at-home order on March 19.

But now nearly 3 in 4 Californians live in counties that have been ordered to reverse their economic reopening, have been recommended to do so or face additional state regulations unless infections flatten out.

As states paused on reopening, former vice president Joe Biden delivered a blistering speech in Wilmington, Del., where he accused Trump of failing to bring the virus under control. Biden, the presumptive Democratic presidential nominee, noted that Trump said earlier in the outbreak that he was a “wartime president.”

“It seems like our wartime president surrendered, waved the white flag and left the battlefield,” said Biden, who, unlike Trump, often wears a mask.

Biden did not wear one during his speech, holding it in his left hand for much of the address. “It didn’t have to be this way,” Biden said. “Month after month, as other leaders and other countries took the necessary steps to get the virus under control, Donald Trump failed us.”

Federal Reserve Chair Jerome H. Powell told the House Financial Services Committee that the economy may be showing signs of progress. But he said that “while this bounce-back in economic activity is welcome, it also presents new challenges — notably, the need to keep the virus in check.”

He said the path ahead for the U.S. economy remains “extraordinarily uncertain” and that the recovery will largely depend on containing the pandemic and reassuring Americans that it is safe to resume their former lives.

Over 10.4 million coronavirus cases have been detected worldwide, with roughly 2.6 million infections reported in the United States. Almost 125,000 people have died of covid-19 in the United States, and the global death count is hovering near 510,000.

The United States is leading the world in officially confirmed infections and fatalities as it continues to see surges in new cases, hospitalizations and deaths in many states.

Of all the states to reverse course, the rollbacks in Arizona were perhaps most notable, given the state’s battleground status in the November presidential election and its role as one of the first states to lift many restrictions in May.

Arizona’s Republican governor reversed course Monday and ordered bars, gyms, nightclubs, movie theaters and water parks to close for at least 30 days, banned gatherings of more than 50 people and told school districts to hold off on resuming classes.

A little over a month after allowing stay-at-home orders to expire, Gov. Doug Ducey on Monday warned residents that “we can’t be under any illusion that this virus is going to go away on its own.”

Arizona hit a high for hospitalizations on Tuesday, at 2,793, and its rolling seven-day average increased by 35 percent.

Public health experts said that while Ducey’s moves made sense, given that the state is inching closer to running out of intensive care beds, some said that they wished he had gone further and instituted a statewide mask-wearing mandate.

“These are effective things to do; they’re going to take some time to show an impact,” said Will Humble, the executive director of the Arizona Public Health Association.

Ducey had opted for an all-in approach to reopening that allowed indoor restaurant and bar patronage right away on May 15, rather than choosing a phased approach like other states. He also supported a Trump rally at a megachurch in Phoenix on June 23, when the president spoke to hundreds of supporters who did not don masks or practice social distancing.

Vice President Pence plans to visit Arizona on Wednesday to meet with Ducey and state health officials. He canceled planned political events with supporters in Arizona and Florida because of the surge in cases.

Delaware Gov. John Carney, a Democrat, said Tuesday that bars at state beaches will close July 3, ahead of the holiday weekend, and remain so indefinitely after a surge of cases in some of those beach towns. In Colorado, Gov. Jared Polis (D) closed bars and nightclubs again as cases in the state spike, the Denver Post reported.

Other states that have reimposed restrictions or put plans to reopen on hold include Texas, Georgia and New Jersey. Cities across the country are tightening their restrictions, too: On Tuesday, Philadelphia halted its plans to allow indoor dining and the reopening of bars and gyms as its coronavirus cases rose.

On Monday, Oregon Gov. Kate Brown (D) said people in the state must wear face coverings in indoor public areas, which was already mandated in eight counties. The statewide order goes into effect Wednesday. And Kansas Gov. Laura Kelly (D) said her mask order will go into effect Friday for people in “public spaces.”

Oregon’s confirmed cases have grown almost every day since May 30 and include a record high of 278 cases on June 16.

Meanwhile, Kansas reported 905 cases over the weekend and six deaths. Overall, 271 have died there since March.

“The evidence could not be clearer: Wearing a mask is not only safe, but it is necessary to avoid another shutdown,” said Kelly, who cited a “significant increase” from clusters where masks were not worn.

Texas set a single-day record Tuesday for new cases with 6,975, public health officials said.

Los Angeles County announced it would close beaches over the Fourth of July weekend and ban celebrations, but it also put a “hard pause” on reopening businesses such as amusement parks and movie theaters, Mayor Eric Garcetti (D) said Monday, after bars were packed over the weekend. The total number of coronavirus cases reported in Los Angeles County topped 100,000 on Monday, and public health experts warn that local hospitals could be facing a shortage of beds within two or three weeks.

New infections have spread since Memorial Day from long-postponed backyard barbecues and bars, which reopened in most counties less than two weeks ago. The number of infections has reached 223,000 in the state, with roughly half concentrated in Los Angeles County.

Garcetti had imposed a stay-at-home order for Los Angeles hours before Newsom extended it statewide. The step, hard on the local economy, appeared to slow the virus before it took on the proportions that New York City faced at the time.

That has shifted sharply. The mayor began loosening the restrictions incrementally in May and lifted the order for bars and restaurants on June 19, despite signs that the number of new infections had begun to rise.

Los Angeles County health officials say 500,000 Angelenos filled bars and restaurants the following day, upending expectations that residents would take the reopening cautiously.

San Diego County, among the state’s most populous, will close its bars Wednesday despite not being on either list. The county announced its own single-day record — 498 — on Monday, and health officials there say the trend is worsening.

Among the biggest fears is the rising hospitalization rate in Los Angeles and other counties.

Hospital capacity had been expanded months ago with makeshift medical centers in sports arenas and, in Los Angeles, offshore on the USNS Mercy. With the virus seemingly contained, the naval hospital ship departed in May.

Barbara Ferrer, the county public health officer, said this week that county hospitalizations have increased 27 percent over the past two weeks. She said the virus could become “a runaway train unless we put the brakes on it.”

Surges in coronavirus cases could put a damper on the Fourth of July holiday as the level of concern about the pandemic among Americans is on the rise again, according to Axios-Ipsos polling.

A poll released Tuesday finds that more than three-quarters of Americans are concerned that their community is reopening too soon, the highest level reached in the Axios-Ipsos surveying.

Meanwhile, nearly 4 in 5 Americans say they consider attending celebrations a large or moderate risk.

Wilson reported from Santa Barbara, Calif.; Gowen reported from Lawrence, Kan. Felicia Sonmez, Amy Goldstein, Michael Birnbaum, Annie Linskey, Rachel Siegel, Jeff Stein and John Wagner contributed to this report.