A physician who headed the intensive care at Baltimore’s Mercy Medical Center has died of the novel coronavirus, a hospital spokesman said Monday.

Dr. Joseph J. Costa, who was chief of the hospital’s Critical Care Division, died about 4:45 a.m. Saturday in the same ICU he supervised. He was attended by his partner of 28 years and about 20 staff members, who placed their hands on him as he died. Costa was 56.

David R. Hart, Costa’s husband, described the moment as painfully surreal when Costa died in his arms surrounded by the people he supervised and worked with.

“Can you imagine taking care of your own son, so to speak, or your brother, if you were a doctor, and going through this? That’s kind of what it’s like when you work at Mercy or any hospital,” Hart, 57, said Monday. “So that’s the hard part for me to watch. He was extraordinary.”

Hart, who also came down with covid-19, the disease caused by the virus, about the same time as his husband, said he had been in awe of Costa’s bravery during the pandemic. As the deadly virus spread, Costa continued to work on the front lines despite having a rare underlying autoimmune disorder. The disease had already sickened another physician and several staff members in the ICU before Costa fell ill in late June, Hart said.

“I begged him not to go to work,” Hart said.

But Costa, who felt it was important to bear the same everyday burdens as his staff — including holiday or overnight shifts — also felt it was important to shoulder the same risks during the pandemic, Hart said.

Hart said his husband’s death also brought home the importance of taking recommended precautions to reduce the virus’s spread — and makes him all the more upset when he sees people flouting guidelines or refusing to wear masks.

“When you see people without masks, you think, ‘Are you out of your mind?’ ” Hart said “This disease will take you out in a heartbeat.”

More than 4.2 million people have been sickened with the coronavirus across the country, and the disease has killed over 145,000. Maryland, Virginia and the District reported more than 2,700 new cases and a dozen deaths on Monday.

The Centers for Disease Control and Prevention, noting that its occupation data is limited, reports that 113,730 health-care workers have been sickened; 576 have died.

Hart, who operated a cafe in Baltimore until retiring a few years ago, said he and Costa met nearly three decades ago this summer through a Baltimore City Paper personal ad. They immediately hit it off.

“That was it. We were never apart after that,” Hart said. “There was just something about him.”

Costa, who spoke fluent German and Italian, loved to travel and played the clarinet, piano and mandolin. Costa was also a Roman Catholic but struggled with the fact that the church was intolerant of his homosexuality, his husband said. But Mercy hospital was not, and its acceptance and daily mission seemed to be the truest expression of a faith that lays emphasis on sacrifice and concern for others, Hart said.

At Costa’s advice, Hart had been staying most of the time at their farm in Shaftsbury, Vt., to reduce his chances of contracting the disease. But when Hart came to visit in late June, Costa started to become ill. When the diagnosis was confirmed, Costa told Hart to leave their Baltimore home at once and return to sheltering in Vermont.

But as Hart drove north, he became sicker and sicker. He sought medical care but was told to self-quarantine because the symptoms still appeared mild. At the farm, Hart monitored his vital signs and remained in close contact with his doctor. But then the disease progressed so rapidly that he passed out. Neighbors found him and called an ambulance.

“I was in denial. I couldn’t believe this was happening to me,” Hart said. “You’re getting sicker, and your whole world is getting smaller.”

Hart recovered. But the disease raged through Costa with even more devastating results, Hart said. Eventually, Costa was put on a ventilator and slipped into a coma.

Costa, who attended the University of Virginia as an undergraduate and studied medicine at the University of Maryland, joined Mercy Medical Center in 1997. He became head of critical care in 2005 and served a two-year stint as the medical staff’s president, hospital officials said. He also chaired the Medical Morals Committee and served as a member of the Mercy Health Services Board of Trustees Mission and Corporate Ethics Committee.

Costa was known for his warm bedside manner, and the nurses and other hospital personnel who reported to him said he acted more like an older brother than a boss, hospital officials said. Plans are underway for a memorial service, they said.

“Joe was more than a trusted colleague,” Sister Helen Amos, executive chair of the hospital’s board of trustees, and David N. Maine, the hospital’s president and chief executive, said in a joint statement to their staff. “He was also a true friend to many. He dedicated his life and career to caring for the sickest patients. And when the global pandemic came down upon us, Joe selflessly continued his work on the front lines — deeply committed to serving our patients and our city during this time of great need.”

Magda Jean-Louis contributed to this report.