SEATTLE — First came handwashing instructions and social distancing. Then came the prohibitions on large events and the shuttering of schools.
Next up, should the coronavirus outbreak grow even more dire, are government measures that could have an even greater impact on daily life.
Washington State — where 31 people have died from the virus, the most in the United States — has escalated through most of a 13-step strategy checklist for controlling infectious outbreaks and now has only a few remaining options: closing workplaces, restricting people to their homes and cordoning off targeted areas to help control the spread of infection.
With new research showing that 400 people in the Seattle area could die in the coming weeks if officials were unable to alter the trajectory of the outbreak, state and city leaders have begun evaluating whether some of those more extreme restrictions may become necessary.
Kevin Wickersham, the incident commander at Washington’s Department of Health, said that none of the options were off the table, but that officials were mindful of the tremendous burden that such restrictions could impose on families and businesses.
“We want to do everything possible to keep society functioning as much as it possibly can,” Mr. Wickersham said.
He said orders to close businesses would be considered only if the virus transmission data showed that such an escalation was necessary. Restricting people to their homes, he said, could be done in a limited way, but not so that it disrupted their ability to get food, medicine or medical treatment. He said local jurisdictions might consider limiting the entry of people into certain regions, but probably only in small areas, perhaps to protect an area with a population that is particularly vulnerable to the disease.
The more draconian measures that loom for state and local agencies have become a rising subject of conversation among political leaders and emergency planners across the country. Gov. Gavin Newsom of California said this week that state officials were running tabletop exercises to simulate strategies for a worsening pandemic — “the kind of plans that keep you up at night.”
Washington State’s decisions so far, which have offered an early window into what may be coming for other states as the virus expands its range in the United States, have been guided by researchers’ emphasis on the benefits of limiting social contact.
In a report made public this week, researchers at the Institute for Disease Modeling, the Bill & Melinda Gates Foundation and the Fred Hutchinson Cancer Research Center concluded that under the current trajectory of the virus, some 25,000 people in the Seattle area could be infected in the next four weeks, and 400 of those might die.
The researchers said that if policymakers could reduce the transmission rate by 75 percent — primarily through social distancing — then only a fraction of those illnesses might manifest and only 30 more people would be projected to die.
Mayor Jenny Durkan of Seattle said those projections helped shape the decisions that were made this week. City leaders announced on Thursday evening the closing of all libraries and community centers, while Gov. Jay Inslee ordered the shuttering of schools in the Seattle area for six weeks.
A day earlier, the governor ordered a ban on all public gatherings of more than 250 people.
Ms. Durkan said she was hopeful that the so-called nonpharmaceutical interventions pursued thus far would be enough to substantially alter the trajectory of the outbreak. She described them as some of the most significant interventions by a government in the United States over the past century. But she said officials would also be watching to see if more needed to be done.
“There’s no good choices, but there are good decisions,” Ms. Durkan said.
In their emergency planning documents, Washington State officials lay out an escalating 13-step strategy to contain an infectious disease outbreak, a playbook that is common to public health officials around the world.
The first recommendation has been heard often in recent weeks: Increase handwashing. But the state has moved through the checklist with wrenching speed over the past two weeks. The Seattle area has already ticked off No. 10, limiting large public gatherings, and part of No. 11, the closing of schools and public buildings, Ms. Durkan noted.
Another part of No. 11 calls for closing workplaces, and No. 12 calls for the government to “prevent nonemergency travel outside of the home.” The final step says: “Establish cordon sanitaire.” Under international health policies, these are controlled zones, guarded by the authorities, to restrict movement into and out of infected areas.
The city of New Rochelle, N.Y., put in place a version of that most serious control measure this week when it established a containment zone around the most affected part of the city.
Kacey C. Ernst, a professor of epidemiology at the College of Public Health at the University of Arizona, said that the United States had a small and closing window of opportunity to act to prevent the further spread of the coronavirus. She said that if the country was able to reduce the speed at which the virus moves to new targets, it would prevent hospitals from becoming overwhelmed.
“We refer to the disease surveillance iceberg — underneath the water’s surface are all the cases that are mild, asymptomatic, untested and unreported,” Ms. Ernst said. “As that iceberg gets bigger, we will see more and more of the tip coming from the surface. This will mean that hospitals will be stretched beyond capacity.”
At the federal level, President Trump has imposed new travel restrictions from Europe, and on Thursday he said that some domestic restrictions, such as limiting travel to hot spots like Washington State or California, might be necessary.
Washington State has led the way in recent days in adopting many public distancing requirements, but cities and states across the country have been imposing restrictions of their own. New York moved to ban most gatherings of more than 500 people, including at Broadway shows. Ohio announced an extended three-week spring break for students. Private organizations have also joined the effort, including major sports leagues and Disneyland, which said it would close its Anaheim, Calif., resort through the end of the month.
Mr. Wickersham said that the United States was in the beginning phases of the outbreak and that evidence suggested that early and decisive action was one of the most effective ways to limit the spread of disease. He also cautioned people to be prepared for long-term life changes, noting that officials were trying to develop models of what the impacts of the disease might be over the course of a year.
“Will there be more interventions and restrictions?” Mr. Wickersham said. “I would say probably.”