New Virus Cases Begin to Slow in U.S. Cities Where Omicron Hit First

At another bleak moment of the pandemic in the United States — with nearly 800,000 new cases a day, deaths rising and federal medical teams deploying to overwhelmed hospitals — glints of progress have finally started to emerge. In a handful of places that were among the first to see a surge of the Omicron variant last month, reports of new coronavirus infections have started to level off or decline.

Daily case reports have been falling rapidly around Cleveland, Newark and Washington, D.C., each of which sustained record-shattering spikes over the past month. There were also early signs in Chicago, New York, Puerto Rico and hard-hit ski resort towns in Colorado that cases were hitting a plateau or starting to drop.

The slowing of the spread in those places was welcome news, raising the prospect that a national peak in the Omicron wave may be approaching. But most of the country continued to see explosive growth in virus cases, with some Western and Southern states reporting 400 percent increases over the past two weeks. Officials also warned that hospitalizations and deaths lag actual infections, meaning that even in places where new cases have begun declining, it would still be weeks before the full impact of Omicron was known.

“We’re very far from being out of the woods,” said Dr. Bruce Vanderhoff, the director of the Ohio Department of Health, who told reporters that he was encouraged by early indications of a downturn in parts of his state. But he warned: “If we’ve learned one thing about Covid it’s that it is extraordinarily unpredictable. And things can change dramatically and quickly.”

It was just seven weeks ago that scientists in South Africa alerted the world to the fast-spreading Omicron variant, and just a month ago that the variant started to gain a foothold in the United States. As cases have soared to record levels in the days since, scientists have found that Omicron tends to cause less severe illness in many people than prior forms of the virus, and that vaccines, though less protective against infection, continue to provide robust defense against critical illness and death.

Still, the speed and scale of the Omicron surge has disrupted American life and taxed a health care system that was already strained by an autumn uptick driven by the Delta variant. Across the country, more than 1,800 deaths are being announced each day, a rise of about 50 percent over the past two weeks. Colleges and some school districts have returned to online instruction, bus routes have been disrupted after drivers tested positive and health care systems have struggled with an uptick of cases among employees.

In Wisconsin, Gov. Tony Evers said on Thursday that National Guard members would train as nursing assistants and then deploy to short-staffed nursing homes. In Omaha, where the Nebraska attorney general sued the county health director over a new mask mandate, a major hospital said it was activating a crisis plan that would limit appointments and reschedule surgeries because of surging caseloads. And at a small hospital in Canton, S.D., officials said, four of the eight nurses who would usually be treating patients on the floor were out with the virus at one point last week.

“What we’re bracing for right now is really doing everything we can to avoid a work force shortage,” said Dr. Jeremy Cauwels, the chief physician for Sanford Health, in the Upper Midwest, where more than 400 employees across the hospital system were off work with the virus this week.

Christina Ramirez, a biostatistician at the University of California, Los Angeles, said it was too early to tell where the United States was in its surge. Omicron passed through and peaked in South Africa in about a month, but countries like Denmark and Germany look more like a “jagged sawtooth,” she said. “You get a couple days where it goes down, goes back up and goes back down.”

“We’ve been fooled by the virus before,” Dr. Ramirez said. “The next couple of weeks will be very telling.”

Even as some cities were seeing new cases slow, reports of infections were continuing to rise sharply nationwide. About 150,000 people with the virus are hospitalized across the country, more than at any previous point of the pandemic. That data includes patients who were hospitalized for other reasons and were found to have Covid.

Several times throughout the pandemic, surges driven by new variants caused cases to rise steadily for a period of time before falling again. Scientists suggest that both biology and behavior help drive that pattern. When cases rise, people may become more cautious, and as more people get infected, the virus will have more trouble finding susceptible hosts. Because Omicron spreads so quickly, this cycle might be faster than earlier surges.

Complicating experts’ understanding of the trajectory of the Omicron surge in the United States have been questions about the reporting of new cases. People have increasingly turned to at-home tests to confirm their infections, and many of those are not counted in official data. But the case trend lines, which as recently as a week ago showed rapid growth almost everywhere in the country, remain helpful in outlining the broad pattern.

In Chicago, Dr. Allison Arwady, the public health commissioner, said on Thursday that she was “much less worried than I was even three, four, five days ago” about the city’s outlook. With cases spiking to record levels in Chicago, a labor dispute between City Hall and the teachers’ union canceled classes for a week. By Thursday, with school back in session, there were signs that reports of new cases and test positivity may be leveling off, even as hospitalizations continued to increase.

“It is still too early in terms of being able to clearly say this is the peak, we’re on the way down,” Dr. Arwady said. “But I think we are seeing some signs of certainly flattening across many different metrics.”

New York City has averaged about 38,000 new infections a day over the past week, down slightly in recent days but still near the highest rate of the pandemic. Gov. Kathy Hochul of New York said this week that it “looks like we may be cresting over that peak,” but that transmission remained high.

At University Hospital in Newark, the number of patients with Covid has held about steady at 150 for the past five days. Dr. Shereef Elnahal, the president and chief executive of the hospital, said he was hopeful that the rapid spike in hospitalizations since late December had finally leveled off.

“With all the caveats, God willing, knock on wood, we are beginning to see a plateau in daily hospitalizations,” Dr. Elnahal said.

Those trends are more pronounced in some other cities. In San Juan, P.R., reports of new cases are down 17 percent in the past two weeks. In the county that includes Cleveland, new case reports have plunged 49 percent in two weeks. Washington, D.C., is averaging 1,700 new cases a day, down from an early-January peak of more than 2,100.

“I believe it’s a true leveling off, though still with horrendous rates of transmission,” said Dr. Lynn Goldman, dean of the Milken Institute School of Public Health at George Washington University.

The slowing of cases in some places did not ease the immediate crisis in many of the country’s hospitals. President Biden said on Thursday that he was sending 120 additional military medical personnel to six states — Michigan, New Jersey, New Mexico, New York, Ohio and Rhode Island — where hospitals had been overrun.

Mr. Biden also said he was directing his staff to purchase an additional 500 million at-home coronavirus tests for distribution to Americans, doubling the government’s previous purchase. It remained unclear when the first of those tests would be available.

Omicron began to surge before Christmas in urban centers in the eastern half of the country, including many of the places where daily caseloads have recently started to fall. But much of the United States, particularly the West and in rural portions of the South and Midwest, did not see a similar spike until around New Year’s. In those regions, daily cases continue to rise swiftly.

In Oregon and Utah, new case reports have increased more than 450 percent in the past two weeks. Los Angeles County, Calif., is averaging about 40,000 cases a day, up from 25,000 a week ago and 5,500 before Christmas. Arkansas, which was averaging fewer than 1,000 cases a day before Christmas, is now reporting more than 7,000 a day. In Louisiana, cases and hospitalizations are both up more than 200 percent over the past two weeks.

“This is not forever,” Gov. John Bel Edwards of Louisiana said. “At some point, we will peak out in this surge as we have previously and we’re going to start coming down the other side, but quite frankly we’re not there yet.”

Whenever the Omicron wave finally recedes, it is uncertain how much protection the nation might have against future outbreaks — whether small and sporadic or more widespread surges.

“I think that’s the million-dollar question,” said Bertha Hidalgo, an epidemiologist at the University of Alabama at Birmingham. “I would hope that we would not see a new variant of concern quickly and the immunity we build to Omicron is long-lasting.”

Evidence from prior variants suggests that immunity from natural infection only lasts so long, Dr. Hidalgo added.

Across the country, officials in places with hopeful glimmers in their data were adopting a cautious approach to interpreting those numbers.

Dr. Ngozi Ezike, the director of the Illinois Department of Public Health, said on Wednesday that it was “too soon to tell” whether the worst of Omicron had passed in her state. Hospitalizations statewide had declined slightly on one recent day, but it was unclear whether that would become a trend.

“You really want to see a consistent decline,” Dr. Ezike said. “I will be the first to announce it when we can say that pretty confidently. Crossing my fingers and toes, but I just don’t want to get ahead of ourselves.”

Michael D. Shear and Tracey Tully contributed reporting.