Dr. Kass recalled that the hospital unit felt “like a pressure cooker,” all of the physicians and nurses doing their best to stay calm as some speculated about what their work would look like once the number of Covid-19 cases surged.

For Dr. Kass, the pressure had been mounting for weeks. She started worrying about coronavirus long before her neighbors were stockpiling toilet paper and news headlines screamed “pandemic.” Last month she sat down to brunch with friends, who asked casually how her work at the hospital was going. “You guys, this is going to touch all of our lives,” she told the group.

Dr. Kass has always been quick to notice threats to public health. She said that’s because for her, her roles as a physician and as a family caretaker are intertwined. Being an emergency doctor makes her a better mom, she said, because she’s always on the lookout for risks that others might miss. Being a mom makes her a better physician because she pays attention to her patients’ unarticulated needs, the emotional, as well as the physical.

But as a doctor, and as a mom, recent weeks have been especially tough. Once news reports began to project a surge of coronavirus cases in New York, Dr. Kass knew that she’d be needed on the front lines. She knew that she’d inevitably be exposed to Covid-19. And she had read that up to 80 percent of clustered infections reported in China were within households, suggesting high intrafamily transmission rates. So she sat down with her three children, ages 12, 10 and 7, and told them that they would need to spend the next several weeks at their grandparents’ house in New Jersey.

It feels unfair, even nonsensical, to be deprived of her source of comfort — her kids — during the most challenging period of her career. But Dr. Kass realizes it’s a sacrifice that comes with her professional territory. “How can we expect health care workers to not hug and kiss their families? But then how can we expect them not to be exposed?” she said. “The choice I made was to not have to look my kids in the eye and say, ‘I won’t hug and kiss you right now.’”