Though the country is conducting far more tests now than it was in the spring, the soaring case numbers now reflect accelerating spread of the virus, not simply wider testing.
Hospitalizations, which give a clear picture of how many people are seriously ill with the virus at any given time, grew by 63 percent over the past month, according to data collected by the Covid Tracking Project. More than 55,000 people are now hospitalized with the virus, approaching earlier peaks of more than 59,000 in April and July.
Treatment has vastly improved since the height of the spring outbreak, when more than 2,200 people were dying per day. Even so, deaths, which tend to lag a few weeks behind new infections, are now trending upward. The country has averaged about 900 deaths a day over the last week, compared with about 700 a month ago.
Mr. Biden is in line to inherit one of the most serious and complicated national crises that any incoming president in more than half a century has faced.
While other presidents have entered office during an economic slowdown, including President Obama and Mr. Biden as vice president in 2009, not since Harry Truman in the final months of World War II has a new president faced a situation as “complex and multiheaded” as the pandemic, said Bruce J. Schulman, a political historian at Boston University.
Mr. Biden has said controlling the pandemic is the necessary first step to bringing back jobs, and has said that on his first day in office, he would move rapidly to appoint a “national supply chain commander” and establish a “pandemic testing board,” similar to Franklin D. Roosevelt’s wartime production panel.
On Sunday, Mr. Biden’s campaign released a first glimpse of his plan for the pandemic, including a commitment to “listen to science.” Public health experts offered initial praise for his coronavirus task force, which is expected to include Dr. Vivek Murthy, a former surgeon general; Dr. David Kessler, a former commissioner of the Food and Drug Administration; and Dr. Marcella Nunez-Smith, a Yale University professor.