State and local officials in Colorado, Idaho, Massachusetts and Texas are imposing new restrictions on schools, businesses and social gatherings, responding to the fall surge in coronavirus infections and hospitalizations that threatens much of the country with a health emergency resembling what struck the Northeast in the spring.

Although this has been a highly politicized pandemic, some of the new restrictions are arising with no regard for local political inclinations: Liberal-leaning El Paso is under a nightly curfew, while conservative-leaning Coeur d’Alene, Idaho, on Tuesday passed a mask mandate.

In Massachusetts, a spike in cases prompted Boston Public Schools to suspend in-person learning last week, and it has forced more than a dozen smaller cities and towns labeled “high-risk” to close businesses, including theaters and roller rinks, and reduce capacity at gyms, libraries and museums.

Rhode Island Gov. Gina Raimondo (D) said at a weekly briefing Wednesday that she would announce new restrictions Friday.

“We’re in a bad place,” Raimondo said. “It’s more than a wake-up call, really, for every single one of us to ask ourselves, ‘What am I going to do differently?’ ”

One forecast published Wednesday, by modelers at Children’s Hospital of Philadelphia, warned that the virus is spreading at exponential rates across at least half of the states and that only Hawaii will not see a rise in hospitalizations during the next four weeks.

“Exponential growth is like what we saw in March and April, and we are now seeing that in half the states in the country,” said David Rubin, director of the hospital’s PolicyLab. “This is like a tidal wave.”

Resistance persists to anything resembling the shutdowns imposed during the frightening viral assault in March and April. But the Children’s Hospital researchers say the trends in infections could soon force many schools, particularly those serving older students, to revert to remote learning until the fall wave passes.

A federal government briefing document circulated to top officials and obtained by The Washington Post rates the 3,141 counties in the country by levels of “concern” and suggests it would be theoretically possible to travel from the Canada border all the way to northern Mississippi without exiting a “sustained hotspot” county.

Another forecast, updated Oct. 22 by the University of Washington’s Institute for Health Metrics and Evaluation, projected that by Nov. 11, the country would once again surpass 1,000 deaths a day from covid-19, the disease caused by the coronavirus. That same projection said the country would exceed 2,000 daily deaths Dec. 28. Those numbers are slightly less grim than the models projected in September, but they still envision close to 400,000 cumulative deaths from the virus by Feb. 1.

Such models are not predictions so much as ways of framing the likely trajectory of the pandemic, assisting the planning of the medical community and government leaders. Infectious-disease experts say the future of the pandemic is not fixed, and human behavior is the key variable.

But the models also show the current rates of infection, already at record levels — averaging above 70,000 newly confirmed cases a day and sometimes rising higher — are likely to increase. Infections are a leading indicator of a likely rise in hospitalizations and deaths.

“It will get progressively worse,” said Christopher Murray, director of the University of Washington institute. “Look at Europe. Europe is about four weeks ahead of us.”

That continent has seen such a dramatic new wave of infections and hospitalizations that many countries are imposing restrictions and mandates to wear facial coverings.

The pandemic is showing clear signs of a fall surge in the Northern Hemisphere, with the coronavirus behaving like other seasonal viruses. That is not wholly unexpected, but the seasonality of the virus had remained essentially hypothetical. There’s little doubt now.

“We believe that what’s happening in the U.S. is the beginning of the fall and winter surge,” Murray said, nothing that last week was the first in which death rates started to climb again. “As soon as you see deaths going up, you know this is a very real phenomenon, and you can’t explain it away.”

Many hospitals in places such as North Dakota and El Paso are bringing in nurses from out of state. But such emergency maneuvers will become harder if, as expected, the high rates of infections continue to rise in dozens of states simultaneously.

“The cavalry can run out. You only have a certain number of people you can ship,” Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases, said Wednesday.

The dire views of the scientific and medical establishment come at a time when many government leaders remain resistant to further restrictions on businesses, schools, sporting events and cultural activities. “Pandemic fatigue” has set in broadly in the general public, along with ideological opposition to mask-wearing and other public health mitigation efforts.

“Things could get seriously much worse because we are in a trajectory going in the wrong direction, and I don’t see anything that anyone’s doing right now that’s going to change that. And that’s what’s really bothering me,” Fauci said.

The pandemic has become such a polarizing topic in the weeks leading up to Election Day that Fauci has received death threats, and his wife and children have been harassed, he said.

“In my wildest dreams, I would not have imagined that something that involves each and every one of us, ourselves, our families, our parents, our children, could not be approached in a uniform way,” Fauci said. “Instead, this triggered a degree of divisiveness the likes of which I’ve never seen.”

Denver Mayor Michael B. Hancock (D) announced new restrictions starting Wednesday, capping capacity at most businesses at 25 percent. He lashed out at people and officials whose laissez-faire responses to the virus, he said, were preventing cities and states from controlling the spread.

“The reality is that states and cities have been left to fend for themselves,” Hancock said in an interview. “If you don’t have a national standard, what you have is a piecemeal approach, and you have absolutely no way of really containing the spread of this virus because people are not going to remain static. They’re going to move.”

He said he knows the new restrictions will have far-reaching implications.

“Thousands, tens of thousands of people out of jobs, furloughed. Families’ lives are disrupted. Children, their education is disrupted,” he said. “That’s why you sense such a frustration in my voice.”

Hancock said he assumed the restrictions would last at least a month, but likely more. Getting case numbers, test positivity and hospitalization numbers down during flu season is daunting, he said.

The city’s school district announced that elementary students in grades three to five, who had returned to their classrooms last week, would go home for online learning starting next week. Middle and high school students would continue distance learning through the end of the year.

Denver’s infection rate has roughly doubled since July. If trends continue, the city’s public health director warned, Denver could face another stay-at-home order.

In Idaho, Gov. Brad Little (R) on Monday signed a health order that limits indoor and outdoor gatherings, requires bars and nightclubs to offer seating-only service and mandates masks at long-term-care facilities. The order, which Little said was intended to curb alarming demand on hospitals and health-care facilities, rolled back reopening rules in effect since mid-June.

Public health officials in the state have attributed much of the surge to social gatherings.

Little, who has resisted calls for a statewide mask mandate, said at a news release that while he still believed in a localized approach to controlling the virus, it “has not worked as well as it should because the virus is relentless and in some parts of the state there have been insufficient efforts by local health boards, mayors and county commissioners to save lives.”

In northern Idaho, the city council of Coeur d’Alene passed the mask mandate after impassioned testimony from the chief executive of the county’s major hospital, who said an eruption of covid-19 cases had recently left the facility with just one available bed. Several schools in the region switched to hybrid learning amid the outbreak.

The city mandate passed days after a district health board rescinded a mask requirement for surrounding Kootenai County and months after Mayor Steve Widmyer expressed opposition to a mandate in his city. On Tuesday, he spoke in favor of it.

“Situations change. We’re in a much different situation 3½ months down the road, where we are today, and we’re in a critical situation right now,” Widmyer said at the council meeting. In the absence of a county mandate, he said, a city rule “is the best that we can do, and for me, doing nothing is not an option.”