Daily coronavirus-related deaths in the United States have reached levels not seen since the early throes of the pandemic following a surge in the number of those hospitalized, an ominous sign that the current jump in cases is beginning to take its deadly toll and that more grim months lie ahead.

On Wednesday, the United States recorded more than 2,200 new deaths — the highest-single day increase since May 6. The figure kept the seven-day average of deaths above 1,600, a figure comparable to that during the first spike in cases and fatalities, and brought the U.S. death total to more than 261,000.

Though far fewer people who test positive for the coronavirus now die of it, the sheer number of those infected has mushroomed in recent weeks. That, in turn, has fueled an increase in deaths, and health experts say the figures could get worse in the months ahead, as family and friends travel and gather to celebrate the holidays, accelerating the virus’s spread.

“Unless we have a sea change in public attitudes and greater adherence to public health control measures, we’re likely to see things worsen,” said Sten H. Vermund, dean of the Yale School of Public Health.

On Wednesday alone, the United States recorded more than 185,000 new coronavirus cases — a figure that dwarfs the daily numbers from May, when at the high point, the United States recorded a little more than 33,000 new cases in a single day.

That is in part due to a significant expansion in testing, but there is little doubt the United States is undergoing its most serious outbreak since the initial surge. That, in turn, creates a head-spinning juxtaposition for many Americans, as promising news about an impending vaccine is emerging at the same time as the rising deaths.

Moderna, Pfizer and AstraZeneca have released promising results from their initial coronavirus vaccine trials. Here are answers to common questions about them. (The Washington Post)

The proportion of deaths among covid-19 patients has fallen, partly because doctors have learned ways of treating the disease and partly because those now getting infected are younger on average.

But those getting infected are flooding hospitals. At about 7 p.m. Wednesday, total hospitalizations stood at more than 89,000, a record. “The challenge is to reduce transmission,” Vermund said. “We’ve got to drive the absolute numbers of cases down.”

Several states and local jurisdictions have tightened coronavirus-related restrictions in recent weeks to try to stem the virus’s spread. D.C. Mayor Muriel E. Bowser (D), for example, announced a ban on indoor gatherings of more than 10 people that took effect Wednesday. Virginia Gov. Ralph Northam (D) earlier lowered the number of people allowed for gatherings indoors or outdoors from 250 to 25 while imposing new limits on restaurants and businesses.

Maryland Gov. Larry Hogan (R) required bars and restaurants to close at 10 p.m. for indoor service and reduced the capacity in a host of other businesses. And the National Football League said it was postponing the Thanksgiving Day game between the Baltimore Ravens and the Pittsburgh Steelers because of coronavirus cases in the Ravens organization.

Joseph Varon, chief of staff at United Memorial Medical Center in Houston, told CNN on Wednesday that his hospital has opened two additional wings to accommodate the influx of patients expected after Thanksgiving. The hospital has been taking patients flown in from El Paso, where the National Guard has been called in to help deal with the large number of bodies.

“If we don’t do things right, America is going to see the darkest days in modern American medical history,” Varon said.

He said some patients are waiting longer to come to the hospital — and therefore arriving sicker — because of what he termed “corona fatigue syndrome.”

President-elect Joe Biden also addressed the notion of coronavirus “fatigue” Wednesday in a Thanksgiving address from Wilmington, Del., urging Americans not to let down their guard out of impatience with the pandemic’s duration.

Bemoaning the death toll, Biden said he and his family were forgoing their holiday traditions and urged others to do so as well, in addition to wearing masks and keeping their distance.

“Each of us has a responsibility in our lives to do what we can do to slow the virus,” Biden said. “Every decision we make matters, every decision we make can save lives. None of these steps we’re asking people to take are political statements — every one of them is based on science, real science.”

Yet the death numbers come at a time when it seems increasingly likely that an end to the pandemic is in sight.

Three pharmaceutical partnerships or companies have announced positive results from late-stage trials of a coronavirus vaccine: Pfizer and its German partner BioNTech, in addition to Moderna, have reported vaccines that were 95 percent effective in clinical trials.

And a vaccine from AstraZeneca was 70 percent effective on average, with up to 90 percent efficacy in a smaller group that got a lower dosage.

Still, the vaccines need approval from the U.S. Food and Drug Administration, and it will take time to produce enough doses to inoculate a significant portion of the population.

The most vulnerable groups, including health workers and the elderly, are expected to get vaccinated first, and that could cut into the number of deaths.

A new study Wednesday found the number of covid-19 deaths in nursing homes and other long-term care facilities has surpassed 100,000 since the start of the pandemic, representing about 40 percent of all U.S. deaths.

“This is an ominous and tragic milestone,’’ said Tricia Neuman, one of the study’s authors and a senior vice president at the Kaiser Family Foundation, a nonprofit focused on health issues that produced the report. She added the figure had been reached “weeks before the surge in new cases that are expected from Thanksgiving gatherings.”

Early distribution of a vaccine, Vermund said, “probably won’t reduce the absolute numbers of cases very dramatically,” because it will be available at first only to the most vulnerable, who aren’t as likely spread the virus as younger, more active people.

He also dismissed the notion that the current growth in cases could mean the United States is on the brink of herd immunity, meaning enough of the population cannot get the disease that its spread is halted. “We’re nowhere near herd immunity,” Vermund said. “We won’t get to herd immunity without a vaccine.”

The current surge is not limited to one area of the country, and Vermund said he was concerned that even some places with high mask usage seem to be seeing spikes.

As of about 7 p.m. Wednesday, five states — Washington, Nevada, Texas, California and Massachusetts — had recorded new one-day highs in cases, while they and 12 others saw their seven-day average in cases hit a new high.

Four states — Ohio, Utah, Iowa and Tennessee — hit new one-day highs for deaths, while nine — Ohio, Utah, Wyoming, Tennessee, Oregon, Wisconsin, Illinois, Missouri and Minnesota — saw new highs in their seven-day average for deaths.

Public health experts have long feared that the coronavirus might surge in the colder months during the traditional flu season, as more people gathered indoors and grew tired of severely limiting their social activities. Officials had hoped they could enter flu season with transmission at a low point, tamped down by public health measures such as mask use, physical distancing and hand-washing.

It is now clear that will not happen, and experts are increasingly concerned about upcoming holiday gatherings, particularly those that are larger in size.

Transportation Security Administration data suggests that Thanksgiving travel is down in recent days compared to last year. But it is still higher than it has been in weeks.

TSA screened more than 912,000 travelers on Tuesday, compared to more than 2.4 million on the same day a year ago.

Still, the previous Tuesday, the agency screened about 611,000 travelers, suggesting that many Americans have chosen to travel for the holiday.

Christopher Rowland and Paulina Villegas contributed to this report.