At the same time, staffing shortages at hospitals in the region have been compounded by a recent increase in infections among their staffs. At F.F. Thompson Hospital in Canandaigua, N.Y., 45 of the hospital’s 1,750 workers were out with the virus recently, and there are 252 unfilled job openings.

“Covid is here, Covid is an issue, but the main challenge up here is the staffing,” said Michael Stapleton, the hospital’s chief executive.

Other hot spots are also putting pressure on health care systems. In Puerto Rico, 245 people on the island were in hospitals this week with the virus, more than five times the caseload from a month ago.

Though hospitalizations generally lag behind the trends in new cases, they remain among the most reliable kinds of data about the pandemic, experts agree — much more so than official reports of positive test results, which experts say significantly understate the true number of infections, especially with the rise of at-home testing. As of Thursday, the average number of new confirmed U.S. cases was almost 68,000 a day, nearly a 60 percent increase over the last two weeks, according to a New York Times database.

Hospitalizations are reported fairly rigorously. “For hospital data, even given that all the people were not admitted because of Covid, we can be sure that the numbers are pretty accurate,” said Dr. Eric S. Toner, a senior scholar at the Center for Health Security at the Johns Hopkins Bloomberg School of Public Health. “So it’s the best data source we have now. The number of new Covid admissions is the number that I pay the most attention to.”

About 11 percent of people hospitalized with coronavirus infections in the United States were in intensive care, as of Wednesday, according to federal data.

The C.D.C. is also keeping a close eye on the nature of hospitalizations. “We’re seeing less oxygen use, less I.C.U. stays, and we haven’t fortunately seen any increase in death associated with them,” compared with earlier periods of the pandemic, Dr. Rochelle Walensky, the agency director, said last week.