In the absence of a White House response, states move to slow infections.

By Ethan Hauser, Mike Baker, Lucy Tompkins and Tracey Tully

In Chicago, a sweeping stay-at-home advisory goes into effect on Monday. Philadelphia is expected to announce new restrictions on movement later in the day. In-person classes for high school and college students in Michigan have been canceled.

From a statewide, two-week lockdown in New Mexico to a new mask mandate in North Dakota, governors and mayors across the United States are taking increasingly stringent steps to slow the coronavirus after a staggering one million cases were recorded in the country over the past week alone. Cases are rising in 48 states.

Dr. Anthony S. Fauci, the nation’s top infectious disease specialist, said on Sunday that 200,000 more people could die by spring if Americans did not more fully embrace public health measures, even with an effective vaccine.

As President Trump has refused to concede the election, Dr. Fauci said health officials had not begun working with the transition team for President-elect Joseph R. Biden Jr. He also said Mr. Trump had not attended a meeting of his coronavirus task force in “several months.”

Dr. Fauci’s warning came as more states announced new measures to limit the spread of the virus.

Michigan will suspend all in-person learning for college and high school students and indoor dining for three weeks, Gov. Gretchen Whitmer said. Other indoor gathering places, like casinos and movie theaters, must also close as part of the order, which takes effect Wednesday.

“This is the worst public health emergency our nation has faced in over a century, and our response has got to reflect the same level of urgency,” Ms. Whitmer said on Sunday as she announced new restrictions.

Dr. Scott W. Atlas, Mr. Trump’s coronavirus adviser, responded to the news of Michigan’s tighter restrictions in a tweet, writing, “The only way this stops is if people rise up. You get what you accept.”

Dr. Atlas, a radiologist, is not an epidemiologist or an infectious disease expert. He has made contrarian arguments, including that the science of mask wearing is uncertain.

In October, officials in Michigan revealed a plot to abduct Ms. Whitmer, who has been the subject of criticism from right-wing protesters for earlier measures she imposed to try to control the virus.

Ms. Whitmer’s announcement came just after Gov. Jay Inslee of Washington said he was ordering fitness facilities and restaurants to stop serving customers indoors, shutting down museums and limiting retail stores to 25 percent of capacity indoors.

As new cases in New Jersey hit a sobering new high over the weekend, with nearly 9,000 reported infections over two days, Gov. Philip D. Murphy announced new gathering limits, bringing the state more in line with New York and Connecticut. No more than 10 people can gather indoors, effective at 6 a.m. Tuesday, down from 25. Outdoor gatherings should not exceed 150 people, starting next Monday. “Particularly with the holidays coming up, we’ve got to plead with people to not let their hair down,” Mr. Murphy said on Monday in an interview with MSNBC.

The governors’ announcements and blunt assessments echoed the stark warnings of Dr. Michael Osterholm, an adviser to Mr. Biden who said the virus was the most dangerous public health crisis since the 1918 influenza pandemic, which killed an estimated 50 million worldwide, including some 675,000 Americans.

“My worst fear is we will see what we saw happening in other countries, where people were dying on the streets,” Dr. Osterholm said on the NBC program “Meet the Press.” “The health care system is breaking, literally breaking.”