As the coronavirus pandemic ravaged New York, the subway and bus system became the lifeline for the city’s emergency response.

But as they served a city under siege, their ranks were battered.

Before the coronavirus, Sally Lutchman’s life read like a love story.

The tale began one Friday night in 2006, when a handsome, smiling stranger caught her eye at a club in Queens. She was 35 and jumping from job to job, but was a regular at this particular joint. That night she and the man, Kris Knight, shared a dance-floor dalliance that left them both breathless.

Three weeks later, they went on a proper date. Before long, they fell in love and sunk into a new life together. She found stable work at the M.T.A. and his business installing garage doors grew. Soon they had two boys, Scott and Logan, and a bustling home on Long Island.

The first signs of the illness arrived on March 11, when Kris, an otherwise healthy 49-year-old, came home complaining of a splitting migraine and chills. He developed a fever that worsened over the next 11 days before he was admitted to Long Island Jewish Medical Center and placed on a ventilator.

To stop and absorb any one of these events could crush a person. So Sally lived in a state of constant motion: She sped through underground tunnels in her train’s operating booth, sprinted to keep up with her children and ran her husband’s business on the weekends.

Then on April 20, around 9:30 p.m., the hospital’s number flashed across her phone’s screen. A doctor explained that Kris had gone into cardiac arrest and had been resuscitated through C.P.R.

Her sister’s parents-in-law had both received C.P.R. at the hospital, she thought. Days later, they were dead.

The hours that followed were murky: She remembers falling to the floor. She remembers calling her sister. She remembers a flood of tears, gasps for breath and her heartbeats reverberating through her chest.

“I literally felt like I was trapped in a dark tunnel without any light,” Sally said.

The next morning, Kris was put on a ventilator for a second time. Because pandemic precautions barred relatives from the hospital, Sally video-called him whenever she could, often with their two boys.

After battling the virus for three months, Kris finally recovered. At home, Sally prepared for an uncertain chapter in their life: Kris would need a chair to use in the shower, a toilet seat with arm rails and months of physical therapy.

But as she drove to pick him up from a recovery center where he spent a month after being released from the hospital, the stress seemed to fade. Over FaceTime, Kris coyly asked Sally if she was dressed up to go meet someone important. “Yeah, I’ve got a date with this guy,” she said, smiling.

Sally stifled tears the moment the two reunited. Embracing his thin frame, she whispered, “I love you.”

A minute later, the two men parted. A week later, his father fell sick. A month later, he was dead.

“We really didn’t think the virus would affect us like that, the way it has,” Cesar Jr. said. “We were wrong.”

Since Cesar Jr.’s childhood, he had seen his father behind a wheel, first as a yellow-cab driver and then as a bus operator. For years, Cesar Sr. urged his son to join him at the transit agency until finally, in 2018, Cesar Jr. became a bus operator.

In March, as the first coronavirus cases were confirmed in the city, that role reversed. As the agency scrambled to issue safety guidelines for workers, Cesar Sr. called his son to ask if he should block the front seats of his bus to better distance himself from passengers. They both should, Cesar Jr. said — it would be safer that way.

The medics rushed his father to Mount Sinai Hospital of Queens. Cesar Jr. paced outside the emergency room door, frantically text messaging with his father to see if the oxygen the doctors had given him was helping.

After his father’s death, Cesar Jr. stayed home alone for weeks trying to understand how the jubilant man he saw waving on Queens Boulevard just a month before was gone. Heartbroken, he pushed everyone close to him — his sister, his girlfriend, his grandparents — away.

As he grieved, Cesar Jr. spent hours outside with a belt sander and angle grinder, carving a handle and welding a blade to turn into a kitchen knife for his grandmother who loves to cook. The knife, he hoped, would become a relic in memory of his father.

“He was gone too soon,” Cesar Jr. said. “There is no reason why he should be forgotten.”

Ninety days are crossed off a calendar hanging below a windowsill. Above it, a faint light filters into the basement apartment. The space is sparse, but signs of the pandemic abound: There are stacks of soap, toothbrushes to scrub fingernails and a table with water bottles and ginger to make immune-boosting tea.

When Pan Chan, a bus operator, moved into the basement of his home in April, he assumed he would live there for a few weeks. The fear of becoming infected on the job and spreading the virus to his parents, wife and five children consumed him.

Living apart from them would help to keep them safe.

Without his usual family life, Mr. Chan kept busy to stave off the loneliness: He drove a B38 bus between Brooklyn and Queens, worked overtime cleaning the bus depot, bought groceries for his family and delivered the food in a socially distanced routine that he and his wife mastered.

But each night, he was back in the basement. Days bled into weeks that melted into months. The strokes of a black pen on his calendar — made diligently at each day’s end — offered the only contours to his self-imposed isolation.

“Relaxation is not part of my life anymore,” Mr. Chan said.

It began on March 9 — eight days after the first case was confirmed in New York — when he decided to move into the basement. He had heard stories about the virus from relatives in China and was hoping to keep his family insulated.

About two weeks later, after some of his colleagues fell ill, Mr. Chan entered his Phase 2: He stopped ordering takeout lunches for fear they could be contaminated. Instead, Winnie cooked him noodles and walked them a couple of blocks to where he stopped along his bus route. The ritual became a rare moment of intimacy between them.

His third — and worst — phase began in early April, on a day so grim he wrote “Challenging Day!” on his calendar. By then, dozens of his colleagues had fallen sick. One bus operator had died. Then the yellow strap on his M.T.A.-issued N95 mask broke, and his supervisor refused to give him a new one.

“You’ve got to deal with it,” Mr. Chan recalled the bus dispatcher telling him.

In June, as New York’s outbreak subsided, Winnie had to return to work and the issues of self-isolation grew more complex. Eventually, she and Pan decided to live together in the basement of their family’s home.

Having Winnie with him is a relief, but some days Pan still wonders how long they can endure this way of life. Then he looks at a note he scrawled the day he moved to the basement in March.

“I couldn’t allow myself to have any regrets,” he wrote. “Regrets are one of the hardest things to live with and also to die with.”