In the doctor’s chest, the pressure spread. His muscles ached, and his breathing grew labored. Then the nausea set in. But he didn’t think he had gotten sick. No, this was panic.

Earlier that day, on March 12, he had called the owner of the primary-care clinic where he worked and demanded that the office reschedule every appointment made by patients without a critical need.

“We have to do it now,” he said, insisting that, with the novel coronavirus rapidly spreading, their office was not equipped to handle infected patients — or prevent them from spreading it, through the clinic, to others. But the owner refused.

“We can’t keep the clinic open and pay people,” the doctor recalled being told, “if we don’t see patients.”

Even when reluctant clients called to ask whether they should postpone, the doctor said, the front-office staff told them not to worry. Come on in.

Horrified, he soon felt overwhelmed.

“It’s when you know you’re hurting people when you took an oath not to,” the doctor said later, speaking on the condition of anonymity because he, like other health-care workers interviewed for this report, feared retribution. “People are not shutting down business — even though they know better.”

While much of the country has fixated on how hospitals will respond to the pandemic, versions of the alarming situation at the physician’s walk-in clinic in Alexandria, Va., are playing out in retail, primary-care and urgent-care clinics across the United States, according to interviews by The Washington Post with health-care workers desperate to warn their patients but afraid that their bosses will retaliate. Thanks to the convenience they provide, these outpatient operations — from family-owned small businesses to sprawling chains backed by venture capital — have flourished over the past 15 years. They now number in the thousands and serve millions of people each year.

Hospitals will, ultimately, provide the intensive care for patients critically sickened by covid-19, the sometimes deadly disease caused by the coronavirus. But often people exhibit no symptoms, or mild ones, during the infection’s early stages, leading many Americans to head straight to the clinics that have replaced personal physicians for physicals and prescriptions, sprained ankles and bouts of the flu.

That means, according to public health experts, the clinics — many of which lack essential safety protocols and protective equipment — have almost certainly become prime locations for the disease to spread, among patients and the professionals trying to treat them.

“Screw the bottom line,” said Ateev Mehrotra, an associate professor of health-care policy and medicine at Harvard Medical School. “This is a public health emergency. Do not put these patients at risk.”

In California, a Bay Area physician at a Kaiser Permanente primary clinic started asking her bosses two weeks ago when they would stop allowing people to come into the office without any prior screening.

“Can we stop the online booking?” she asked. “When are we going to change this?”

Then she got a fever and started feeling short of breath. She quickly self-quarantined at home and was eventually tested for the coronavirus. The results still haven’t come back.

Soon after, her clinic and others run by Kaiser ceased online booking and shifted to a “telehealth” model, allowing staff members to screen and treat patients through phone or video calls.

The doctor appreciated the move but has continued to hear from colleagues nationwide whose clinics have resisted making such a change — largely, they have told her, because of money. The doctor called that reality “intensely frustrating.”

At a CVS MinuteClinic in the Washington region, a nurse practitioner understands that feeling well.

The staff at her MinuteClinic — one of more than 1,100 in the United States — continue to give people flu and strep swabs that force them to cough. Until this week, the nurse practitioners and physician assistants performing those procedures did so while wearing nothing more on their faces than basic surgical masks, which provide far less secure protection than the gold-standard N95 masks.

“I don’t feel like management is taking into consideration our exposure rate,” the nurse said. “I just feel like CVS is more concerned about making money than the safety of the community and our providers and staff.”

Though those providers at the MinuteClinics began requesting better protective equipment earlier this month, the N95 masks arrived at the nurse’s location only this week. The company also just eliminated waiting areas, where customers often sat just inches apart.

“The health and safety of our MinuteClinic providers, store colleagues and patients is our primary focus,” company spokesman T.J. Crawford said in an email to The Post. “We’re in constant contact with our providers about the appropriate use of protective gear and are distributing supplies as quickly as possible.”

Even with the revised waiting-room guidelines and new equipment, the nurse said, she does not think that’s enough. Anyone can make an appointment online, and though CVS’s website warns that the clinics cannot test for the coronavirus, she said the clinic is still seeing patients with upper-respiratory symptoms who might pose a danger. The woman and her co-workers then have to treat those people in small, unventilated spaces where it is impossible to stand six feet away from someone. The nurses and physician assistants, who at busy times see new customers every 20 minutes, must also clean the rooms between consultations.

What if, in their rush, they miss a spot?

“Our clinic is not designed to cater to this,” she said. “I don’t see it being a safe place for people to go right now.”

On the other side of the country, a health-care worker made a similar case about a group of outpatient clinics near Olympia, Wash., run by Providence Health and Services. In a place just 70 miles from King County — where the coronavirus had infected more than 650 people and killed at least 60 as of Thursday — the person said Providence’s clinics are “grossly unprepared” for the pandemic.

Though the N95 masks have been hard to procure nationwide, the clinics’ managers have told staff members they do not need them, according to the health-care worker.

Administrators, this person said, are operating under the assumption — which the Centers for Disease Control and Prevention describes as “currently uncertain” — that the coronavirus cannot be spread in the air through microscopic droplets known as aerosols, a belief that researchers now say may be false.

“They’re not weighing the uncertainty and the risk, and, most importantly, they’re not being transparent about doing that,” the worker said.

The person raised a number of other serious concerns — that the people who have been assigned to screen patients at the door for symptoms of the coronavirus (and send the ones who do not appear to be infected to a specially designated clinic) are less experienced staff members who have not received sufficient triage training; that some patients with fevers and coughs who show up at the clinic meant for non-ill customers lie their way in, potentially exposing healthy staffers and visitors; that nonessential appointments are not being canceled; that, at times, more than 10 staff members wearing no masks are still packing into tight office spaces — “elbow to elbow, almost” — despite the CDC’s warning not to do that.

In a statement, Providence spokesman Chris Thomas disputed none of those allegations, instead saying the nonprofit organization was doing its best to gather protective equipment and stating that it was working to ensure its staff “will continue to provide high-quality, compassionate care for the patients who need us in this time of increased need.”

Perhaps most concerning to the staff member was another point the statement did not address: The worker said Providence has been slow to ramp up virtual care — which allows doctors and nurses to speak to patients through video calls — because the organization appears too disorganized and because it can charge more for in-person visits.

“People have to understand that we’re seeing these patients when they’re the most contagious,” the person said. “We are not protecting our health-care workers at the highest level possible.”

Transitioning to telemedicine can be a challenge for many clinics, especially smaller ones that operate with limited technological expertise or on tight budgets, said Michael L. Barnett, an assistant professor at the Harvard T.H. Chan School of Public Health. But now, he said, is not the time for financial considerations to dictate any approach to treatment.

“If health-care providers do get sick, just think of the range of people they’re going to get sick,” argued Barnett, whose clinic in Boston has shifted to virtual care. “They just seed the entire region with potential infections.”

That is what the doctor at the Virginia clinic feared he and his colleagues would do as he pleaded with his boss to intervene. In retrospect, he suspected that patients with covid-19 had been coming in for care for at least three weeks.

Without access to an N95, he put on a surgical mask and stood at least six feet from his patients, then implored them not to come back again.

“The only safe medical thing for me to do is sit in front of the office and tell my patients not to go in,” he said he thought at the time. “That’s the only ethical thing to do right now.”

Fearing he would be fired and sued, the physician didn’t do that, but on Friday, he expressed his grave concerns in a Facebook post. That evening, after work, he got an angry text message from his boss.

“I was told you had complained to the health department, ” one message read. “Today was unfortunately a very stressful day for the whole staff caused by you. I just want to make sure that behavior does not continue in any manner.” The owner then asked that, if the doctor planned to come in the next day, “please make sure there is no commotion.”

“It is very stressful for me when my front desk on your orders are giving advice exactly contrary to mine,” the doctor wrote back. “It is very stressful for me that I am violating my Hippocratic oath by continuing to see routine patients and accelerating this pandemic. How should we resolve this?”

The physician told the owner that he would still come in the next day but added one more point: “Just documenting that on this day I advised you in writing to reschedule patients who do not need to come in (refills, etc that we can call in, physicals, etc.) and that your company has declined to follow the recommendation of its medical director.”

On Sunday, the physician received a message telling him he would be taken off the schedule for “causing mayhem.” Then, after that, the owner changed his mind, allowing the doctor to see patients over video calls.

But on Saturday, the doctor went back to work, as he had promised.

That day, a person who had read the physician’s Facebook post came into the clinic, but not because the man needed anything. Instead, he wanted to give the doctor something — a new mask.

Ian Shapira and Katie Mettler contributed to this report.