It was the flyers bearing his photo that made Adam Witt suspect something had gone deeply wrong. Last week, Jersey Shore University Medical Center, where he worked as a nurse, posted the flyers at two security stations, declaring that he was persona non grata.

“Mr. Witt is not allowed on property at JSUMC,” the writing said, beneath a picture of him looking tired and pained. “If he is seen on property please contact your supervisor immediately.”

The troubles had started when Witt, the local nurses’ union president, learned that a fellow nurse had been disciplined for raising concerns on a private Facebook page about coronavirus exposure at the hospital. Witt told his manager that he would be taking a day off to defend the nurse at a disciplinary hearing, a task that he and other union officials had carried out numerous times under their contract. The hospital says a supervisor suggested that Witt skip only part of the day because of the surge in patients.

A week later, on March 31, the hospital said he was being suspended because the day he took was unauthorized. The flyers soon followed.

“It’s not what they normally do in these cases,” Witt said in an interview. “You don’t get ‘wanted’ posters.”

He was fired after a disciplinary hearing Monday. His employer cited the absence, but he believes that the firing stemmed from his persistent questioning of the administration during the pandemic, including through his own social media posts.

As the coronavirus crisis has escalated, workers as varied as grocery cashiers, customer service representatives and flight attendants have clashed with the employers they accuse of failing to protect and properly value them. Amazon drew attention when it fired a worker who had led a protest over health concerns at a Staten Island warehouse.

But perhaps the most curious and persistent management-labor tension has arisen between health care providers like doctors and nurses, who are at the forefront of the virus battle, and the administrators they report to.

In New York City, the epicenter of the crisis in the United States, every major private hospital system has sent memos in recent weeks ordering workers not to speak with the media, as have some public hospitals.

One system — NYU Langone Medical Center, which has more than 30,000 employees at six inpatient centers, dozens of outpatient facilities and the New York University School of Medicine — sent an email March 27 warning that staff members speaking to the media without permission “will be subject to disciplinary action, including termination.” The email was reported earlier by Bloomberg.

Administrators suggested “appropriate” posts on social media instead. “Please share positive and uplifting messages that support your colleagues and our organization,” they said in another email.

Similar lines are being drawn nationwide. A doctor in Washington state was removed from his hospital position after speaking publicly about a shortage of protective equipment and testing; the staffing firm that employs him said he was being reassigned. Nurses in Detroit recently walked off the job to protest critically low staffing after a colleague who had spoken up on the issue was fired. A union representing an Oregon nurse says she was told she would face disciplinary action after being quoted in the media, though the hospital did not follow through.

“They’re very protective of their reputation in the community,” said Jhonna Porter, a nurse who was suspended from West Hills Hospital in Los Angeles after raising safety concerns in a private Facebook group and publicly on her own page, including appeals for equipment. “If anything seems like it might make them look bad, they’re going to stomp on it quick.”

Porter was reinstated Wednesday after media reports about the conflict. In a statement, the hospital said she had created privacy concerns by posting about “specific information, including room numbers of possible COVID patients, to a Facebook group that included former employees.” It said it had determined that the violation of policy was inadvertent and that she had been reinstated with no disciplinary action taken or loss of pay.

Philip Martin Rosoff, an emeritus professor at Duke University School of Medicine who headed the hospital ethics committee there, said that hospitals had become more corporate over the decades and that their executives consequently had the same impulses as other executives to “control the narrative.” However, he said, hospital officials have other reasons to be wary of doctors and nurses who take matters into their own hands, such as patient safety. He cited the refusal of some surgeons to treat HIV-positive patients at the height of the AIDS epidemic.

Perhaps nowhere is the friction between health workers and management more palpable than in the New York area.

A doctor at Lincoln Medical and Mental Health Center in the Bronx, Deena Elkafrawi, was reprimanded after the British publication Metro quoted her as saying, “I am scared that going to work could kill me,” according to the Committee of Interns and Residents, a national association that represented her. Lincoln did not respond to a request for comment for this article.

Other health systems, including Northwell Health, NewYork-Presbyterian Hospital and Montefiore Medical Center, have barred workers from speaking to reporters, though not always with the explicit threat of termination.

“Do not respond or speak to any reporters, as well as current or former employees, regarding a pending news story,” wrote David Feinberg, chief marketing and communications officer at the Mount Sinai Health System, in an email to all faculty and students March 26. Mount Sinai has more than 40,000 employees.

There has been internal dissent as well. Tasha Smith, a Mount Sinai nurse, said she had been fired after complaining to her boss that she was uncomfortable treating coronavirus patients without proper equipment and said she had brought a doctor’s note attesting to her anxiety. Mount Sinai said in a statement that Smith had been fired ​because “without any notice, she walked off the job.” It also said it always provided its medical staff with the equipment needed “to safely do their job.”

Smith, who had worked at the hospital for three years, said the abrupt firing frightened fellow nurses. “They’re afraid to speak up,” she said. “I was made an example of.”

On Friday, several New York City Council members announced plans for legislation to prohibit firing health care workers for speaking publicly about hospital conditions.

“They have the guts to speak up to improve the larger issue, and the reward that their employers give them is to be fired or sent gag orders or threats. It’s unconscionable,” said Councilman Brad Lander, D-Brooklyn, who is a primary sponsor.

Few health systems appear to have gone to the lengths of Witt’s employer, Hackensack Meridian Health, a New Jersey-based chain of 17 hospitals and a variety of other facilities that reported $6 billion in revenue in its 2018 annual report.

Witt, who retrained midcareer to become a nurse after seeing the devastation of Hurricane Katrina in 2005, said labor relations at the hospital had been strained for several years. But he and two other Jersey Shore nurses said tensions had escalated substantially since the onset of the pandemic, in which New Jersey has been one of the states hardest hit. More than 150 patients with the virus have been taken to the medical center so far.

Witt and his colleagues said they previously had direct access to senior hospital officials, including the chief nursing officer. In recent weeks, however, the administration has stopped responding to direct inquiries, requiring them to communicate through a human resources official, they said.

“As they built these walls, we have less ability to bring concerns forward,” Witt said. “It’s like they decided it was martial law in a crisis.”

A hospital spokeswoman said that “as a result of senior leadership’s need to be on the front line during this unprecedented pandemic, we knew unfettered access was not tenable, so we offered this alternative.”

The issue of protective equipment has been particularly fraught. Witt and other nurses said the administration had kept N95 masks — which block most airborne particles — locked in an office, rationing them tightly and making them difficult to obtain in an emergency.

“In a time like this, we need honesty,” Witt said. “‘This is how many N95s we have. We can give you this many for your shift. You all decide what makes sense.’” Instead, he added, “they stopped answering us.”

Daniel Varga, the chain’s chief physician executive, said in an interview that the masks had been locked down because they were disappearing from hospitals on a regular basis, which “puts front-line caregivers at risk.”

Witt also took to social media to talk about shortcomings in personal protective equipment, hazard pay and other issues, including one Facebook post that was shared more than 400 times.

Witt said that by the time he was suspended, the hospital appeared to have lost its patience and was “sort of throwing the book at me.” He provided documentation showing that he emailed his manager informing her of the union day and shared language from the contract that provides for 26 such days per year. He said that he had never been told he couldn’t take the day off and that even if the day had been unexcused, it would not typically merit a suspension or termination.

A Hackensack Meridian spokeswoman said that the hospital had the right to deny a request based on patient needs and that in addition to his absence, Witt “showed abusive behavior” by threatening to text the chief nursing officer hourly in late March after a human resources official did not respond to a query.

“For the safety of staff and patients, security had to be alerted to not let him on the premises,” the spokeswoman said, alluding to the flyer featuring his picture, which she said had been posted out of public view.

Witt said he had filed an appeal of his termination, which will require another administrative hearing. The case could end up before an arbitrator. In the meantime, he will remain president of the local union, across the bargaining table from management in a coming contract negotiation.

“I don’t know if that occurred to them that I’ll be union president, still representing people,” he said. “Now this is all I have to do.”