Covid hospitalizations are surging, but a smaller proportion of cases is severe compared with previous waves. With staff shortages, some hospitals are still in crisis.In hospitals around the country, doctors are taking notice: This wave of Covid seems different from the last one.Once again, as they face the highly contagious Omicron variant, medical personnel are exhausted and are contracting the virus themselves. And the numbers of patients entering hospitals with the variant are surging to staggering levels, filling up badly needed beds, delaying nonemergency procedures and increasing the risk that vulnerable uninfected patients will catch the virus.But in Omicron hot spots from New York to Florida to Texas, a smaller proportion of those patients are landing in intensive care units or requiring mechanical ventilation, doctors said. And many — roughly 50 to 65 percent of admissions in some New York hospitals — show up at the hospital for other ailments and then test positive for the virus.“We are seeing an increase in the number of hospitalizations,” said Dr. Rahul Sharma, emergency physician in chief for NewYork-Presbyterian/Weill Cornell hospital. But the severity of the disease looks different from previous waves, he said. “We’re not sending as many patients to the I.C.U., we’re not intubating as many patients, and actually, most of our patients that are coming to the emergency department that do test positive are actually being discharged.”Though it’s still early for firm predictions, the shift in hospital patterns fits with emerging data that Omicron may be a variant with inherently milder effects than those that have come before, less prone to infecting the lungs, where it can cause serious disease. But the lower proportion of severe cases is also happening because, compared with previous variants, Omicron is infecting more people who have some prior immunity, whether through prior infection or vaccination. The vast majority of Omicron patients in I.C.U.s are unvaccinated or have severely compromised immune systems, doctors said.Hospitals, facing staff shortages, are under enormous strain. In New York City, hospitalizations have exceeded the peak of last winter’s surge. And Governor Larry Hogan of Maryland declared a state of emergency on Tuesday, noting that the state had more hospitalized Covid-19 patients at that time than at any previous point during the pandemic.“We’re in truly crushed mode,” said Dr. Gabe Kelen, director of the Johns Hopkins University School of Medicine’s emergency department.The number of I.C.U. patients is a lagging indicator, likely to rise in the coming weeks, experts said. What’s more, some states are still struggling under the crush of hospitalizations from Delta, a previous version of the virus that may be more virulent. (Hospitals are frequently in the dark about which variant newly admitted patients are infected with.)Still, several reports suggest that Omicron is a foe different from the variants that came before. And the challenges hospitals face — at least so far — are less about stockpiling equipment and more about staffing and contagion, doctors said.“Early on in the pandemic, we were worried about running out of things, like ventilators,” said Dr. Ryan Maves, an infectious disease and critical care physician at the Wake Forest School of Medicine in Winston-Salem, N.C. “Now, the real limitations are obviously physical bed space, but even more so, it’s staffing.”When reports emerged in early December that hospitals in South Africa were handling relatively few severe Omicron cases, experts stressed that the findings should be interpreted with caution. South Africa has a relatively young population, and a large proportion had been infected by previous waves, leaving the affected people with some pre-existing immunity.But now that the virus has spread across the world and the United States, there is more evidence that many people who have been infected with Omicron in recent weeks seem to be faring better than those who were infected with other variants or during earlier surges.An empty waiting room outside the Covid I.C.U. at Covenant Healthcare in Saginaw, Mich., last month. While the number of I.C.U. patients is down, it is a lagging indicator, experts said.Isadora Kosofsky for The New York TimesIn Britain, people with Omicron were about half as likely to require hospital care and one-third as likely to be admitted to the hospital from emergency rooms than those infected with Delta, according to a government report released last week. Early reports from Canada suggest a similar pattern.And a new report from the Houston Methodist health care system, which has been sequencing the vast majority of viral samples from its patients since February 2020, found broadly the same thing.By Dec. 20, the new variant was causing more 90 percent of new Covid cases at Houston Methodist. In the new analysis, researchers compared 1,313 symptomatic patients who had been infected with Omicron by that date to Houston Methodist patients who had been infected with the Delta or Alpha variants beginning earlier in the pandemic.The numbers of Omicron cases examined in Houston are small, and it takes time for the worst outcomes to manifest. But fewer than 15 percent of those early Omicron patients were hospitalized, compared with 43 percent of the Delta patients and 55 percent of the Alpha patients, the study found.Among those who were admitted, Omicron patients were also less likely to require mechanical ventilation and had shorter hospital stays than did those infected with the other variants.“On average — and I’m stressing on average — the Omicron cases are less severe,” said Dr. James Musser, the chair of pathology and genomic medicine at Houston Methodist, who led the research. He added, “And that’s obviously good news for our patients.”The Omicron patients were also younger, and more likely to be vaccinated, than were those with previous variants, which may partially account for the milder illness.Although the reports are encouraging, it is still too early, and there is not yet enough detailed data, to draw firm conclusions about Omicron’s inherent severity, said Natalie Dean, a biostatistician at Emory University in Atlanta.“There hasn’t been really quite enough time,” Dr. Dean said. It took months for numerous large studies of Delta’s hospitalization risks to appear.In New York City, cases have been steadily rising since December and are now overwhelmingly accounted for by Omicron. Covid hospitalizations have also increased sharply, and I.C.U. admissions have been rising more slowly.At New York University’s Langone Health, for example, around 65 percent of patients admitted with Covid were “incidentally” found to have the virus, and their hospitalizations were not primarily because of the illness. At NewYork-Presbyterian, just under half of Covid admissions were incidental.Hospitals in other cities have also been reporting higher rates of incidental infections. Across Jackson Health System hospitals in Florida, 53 percent of the 471 patients with Covid were admitted to the hospital primarily for other reasons. At Johns Hopkins Medicine in Maryland, 20 percent of patients seeking treatment for non-Covid complaints are testing positive for infections, said Dr. Kelen of Johns Hopkins.The Coronavirus Pandemic: Key Things to KnowCard 1 of 3The global surge.