One doctor dreamed he was surrounded by coughing patients. “Most physicians have never seen this level of angst and anxiety in their careers,” a veteran emergency room doctor said.

SEATTLE — After her shifts in the emergency room, one doctor in Utah strips naked on her porch and runs straight to a shower, trying not to contaminate her home. In Oregon, an emergency physician talks of how he was recently bent over a drunk teenager, stapling a head wound, when he realized with a sudden chill that the patient had a fever and a cough. A doctor in Washington State woke up one night not long ago with nightmares of being surrounded by coughing patients.

“Most physicians have never seen this level of angst and anxiety in their careers,” said Dr. Stephen Anderson, a 35-year veteran of emergency rooms in a suburb south of Seattle. “I am sort of a pariah in my family. I am dipping myself into the swamp every day.”

As the coronavirus expands around the country, doctors and nurses working in emergency rooms are suddenly wary of everyone walking in the door with a cough, forced to make quick, harrowing decisions to help save not only their patients’ lives, but their own.

The stress only grew on Sunday, when the American College of Emergency Physicians revealed that two emergency medicine doctors, in New Jersey and Washington State, were hospitalized in critical condition as a result of the coronavirus. Though the virus is spreading in the community and there was no way of ascertaining whether they were exposed at work or somewhere else, the two cases prompted urgent new questions among doctors about how many precautions are enough.

“Now that we see front-line providers that are on ventilators, it is really driving it home,” Dr. Anderson said.

Doctors, nurses and other staff members in a variety of hospital departments face new uncertainty. In intensive care units, for example, health care providers must have extended exposure to people who have contracted the virus. But they know in advance of the risk they face.

In emergency departments, the danger comes from the unknown.

Patients arrive with symptoms but no diagnosis, and staff members must sometimes tend to urgent needs, such as gaping wounds, before they have time to screen a patient for Covid-19, the disease caused by the virus. At times, the protocols they must follow are changing every few hours.

“Many of us have trained for disasters, like Ebola and hurricanes,” said Dr. Adam Brown, the president of emergency medicine for Envision Healthcare, the largest provider of contract physicians to emergency rooms. “This is different because of the scale and scope of the disease.”

Add to that the shortage of protective gear and delays in testing, and health care workers fear they are flying blind.

Though the numbers are still low, Envision, which employs 11,000 emergency clinicians across the United States, has five times as many doctors under quarantine as it did a week ago, Dr. Brown said.

Several providers spoke on the condition of anonymity because their employers have told them not to talk to the news media.

The personal strain is cascading as the virus reaches new parts of the country. “Everybody feels the stress, but everybody is pulling together,” said Dr. K. Kay Moody, an emergency room doctor in Olympia, Wash., who runs a Facebook group with 22,000 emergency physicians. “That is what is keeping us OK.”

A few doctors said they were talking about bunking up in Airbnbs to create “dirty doc” living quarters to avoid endangering their children when they go home. Some are showing their partners where to find their passwords and insurance, should they end up in intensive care. Dr. Moody said she knew of at least one doctor whose former spouse was threatening to take their children away if the doctor went to work.

Many emergency physicians work as contractors, not hospital staff, so they will not necessarily be paid if they are quarantined. “As it stands, that is one of the most anxiety-provoking things,” Dr. Moody said, “on top of fear for your life.”

Nurses face similar challenges, though with less pay and support. An emergency nurse in Milwaukee said she bought her own goggles after hearing that protective gear was running low. A nurse at a rural hospital near Lake Tahoe in California said that the hospital was providing physicians with shower facilities as well as clean scrubs to wear, but that nurses had to wash their work clothes at home. She said that the physicians she worked with lobbied the hospital to provide clean scrubs for the nurses, but that the hospital concluded it would cost too much.

One doctor, who spoke on condition that the identity of the veterans hospital where she worked was not revealed, said the protocols have not kept up with the changing reality on the ground. When determining if a patient should get a separate room, she said, the emergency department still asks patients if they have been to high-risk countries, like China and Italy, even though community transmission of the virus has been well established.

Doctors have begun building plans for how they will ration supplies when there are more patients than their hospitals can handle. Emergency room doctors have experience sitting families down to advise discontinuing care because it would be futile. But in the United States, they are not used to making such calls based on resources alone.

Some said they were looking to Italy, where doctors on the front line have sometimes had to ration care in favor of younger patients, or those without other complicating conditions, who are more likely to benefit from it.

“If we get it all at once, we don’t have the resources, we don’t have the ventilators,” said Dr. William Jaquis, chair of the American College of Emergency Physicians.

Last week, Italian media reported that Bergamo, a city northeast of Milan, saw roughly 50 doctors test positive for the virus. In the region of Puglia in the south, local media reported that 76 employees had been quarantined after being exposed to patients who contracted Covid-19.

After the coronavirus broke out at a nursing facility near Seattle, Dr. Anderson sat with the leaders of his hospital, MultiCare Auburn Medical Center, to talk about how urgently they should prepare. Their hospital is ringed by nursing homes and other care facilities, and he rattled off those most at risk for fatal cases of the virus: males over 60, and those with cardiac and pulmonary problems. “I literally stopped what I was saying and realized that that was me,” he said.

He said his hospital was down to a two-day supply of surgical masks — he wears one per shift. “Those are supposed to be disposable,” he said. Now he must carefully remove and clean the mask each time he takes it off and on. “That may sound just like a nuisance, but when you’re potentially touching something that has the virus that could kill you on it, and you’re doing it 25 times a shift, it’s kind of nerve-racking,” he said.

His wife has moved to their mountain cabin, and they have given up on their retirement cruise in Europe. “I haven’t slept for longer than three hours in the past two weeks,” he said.

In the early hours of Monday morning, he could not sleep. More than 200 emails had come into his inbox since he went to bed, including news that three other health care providers had been admitted to a hospital overnight, he said.

But he plans to be at his next shift nonetheless.

“I have been doing this for 35 years,” he said, “and I’m not going to stop now.”