The U.S. state of California hit another milestone Sunday in its struggle against an unprecedented surge in coronavirus cases, reporting more COVID-19 patients in state hospitals now than at any other point during the pandemic. Health experts, in the meantime, have warned Americans to expect that sharp rise in cases to continue, due in part to the Thanksgiving holiday – potentially worsening heading into the December holiday season.

The number of new COVID-19 cases reported in the United States topped 200,000 for the first time Friday, according to data from Johns Hopkins University. Since January, when the first infections were reported in the U.S., the nation's total number of cases has surpassed 13 million. More than 265,000 people have died. The country passed four million cases of the coronavirus for November on Saturday, more than double the record 1.9 million cases set in October.

Both statewide and in L.A. County, average daily coronavirus cases have quadrupled in recent weeks and hospitalizations have tripled. There were 7,415 COVID-19 patients in California hospitals as of Saturday, according to the most recent numbers released by the state. The largest number was in L.A. County, which reported 2,185 patients. Average daily deaths are also significantly up – tripling in L.A. County and close to doubling statewide in recent weeks.

The surge has sparked a race in the county to tamp down the increase in cases before a wave of hospitalizations overwhelms the health care system. County health officials have announced a series of new restrictions in rapid succession over the past two weeks as the numbers have continued to shoot up.

Last month, California became the second state to eclipse 1 million known cases after Texas. The timeline of COVID-19 in the U.S. begins in California. The state had some of the earliest known cases among travelers from China, where the outbreak began. The Feb. 6 death of a San Jose woman is the first known coronavirus fatality in the U.S. That same month, California recorded the first U.S. case not related to travel and the first infection spread within the community.

COVID-19 has infected nearly 63 million people worldwide, with more than 1.4 million deaths.

The U.S.'s top infectious disease expert said Sunday that the U.S. may see "surge upon a surge" of the coronavirus in the weeks after Thanksgiving, and he does not expect current recommendations around social distancing to be relaxed before Christmas.

Meanwhile, in a major reversal, New York City Mayor Bill DeBlasio said the nation's largest school system will reopen to in-person learning and increase the number of days a week many children attend class. The announcement came just 11 days after the Democratic mayor said schools would shut down because of rising COVID-19 cases. "We feel confident that we can keep schools safe," he said. New York City was the early epicenter of America's coronavirus pandemic, but hot spots have since popped up across the country, leaving practically no region unaffected.

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, told ABC's "This Week" that the level of infection in the U.S. would not "all of a sudden turn around." "So clearly in the next few weeks, we're going to have the same sort of thing. And perhaps even two or three weeks down the line ... we may see a surge upon a surge," he said.