NEW YORK (NYTIMES) - In March, when it became clear that New York City would become a Covid-19 hot spot, Elaine Yang and David Weir panicked over how to take care of their daughters: Ainsley, three, and Adeline, one.

Yang, 39, is an anaesthesiologist at the Hospital for Special Surgery with a specialty in critical care medicine, and Weir, 49, is a critical care medicine pulmonologist at New York-Presbyterian Lower Manhattan Hospital and Weill Cornell Medical Centre. They did not want their nanny, who is over 50, to risk her health travelling across New York City each day, so they paid her to stay home.

Naturally, Yang and Weir wanted their daughters to remain in Manhattan. But what if one of the two doctors contracted the coronavirus on the front lines of a pandemic? Yang expected to work in an intensive care unit like Weir, and neither could juggle strenuous ICU shifts and raise the girls alone. What if they both tested positive for Covid-19, or worse, died? The possibilities petrified them.

Faced with this issue, some New York City doctors sent their children to stay with family in neighbouring states. However, Yang's parents lived in her native Taiwan and Weir's relatives, in New Jersey and Ohio, have health issues that would put them in danger of complications from Covid-19.

So Yang's older sister, Heather Carmichael, offered to take the girls. She and her husband, Alexander, had the space, a housekeeper to help out and two sons who loved playing with Ainsley. There was only one catch: They lived in Singapore.

"At the time, Singapore was relatively well-controlled," Yang said. "They didn't have a lot of cases, and there were no restrictions on travel. We thought it was possible it would only be for a few weeks."

But then a nightmare scenario unfolded that they had not anticipated.

After Yang got the girls settled at her sister's home and returned to New York, Singapore's government issued a partial lockdown and closed its borders to foreigners and travellers in transit as its coronavirus caseload more than doubled.

From late March to early May, the couple focused only on work. Yang alternated between an ICU at Weill Cornell Medical Centre and one at the Hospital for Special Surgery. She worked weekends and regularly switched from day shift to night shift with little rest in between. When Weir and Yang saw each other, it was in passing. They sent supportive text messages and prepared each other meals, but Yang said she still felt lonely.

"It was traumatic," she said. "You'd work 18 hours and then eat dinner in the kitchen by yourself, but you don't let yourself feel how miserable you are because you just keep thinking, 'Oh, my God, what am I going into at the hospital tomorrow?'"

Weir placed a bed in his office and, for a stretch, only went home to shower. He said he fell into a routine: Wake up, FaceTime with the girls, work for 14 hours, eat standing up, get some sleep and do it again.

"We were seeing people our age, who have kids, dying in the hospital from Covid-19," Weir said. "It was terrifying."

Weir and Yang had met at New York University in 2007 and found they had a lot in common, including the same birthday. He was a resident, and Yang, who immigrated to the United States at seven, was in her final year of medical school. They pursued their careers on separate coasts but stayed together, eventually returning to New York City and marrying in 2012.

In May, as New York City's Covid-19 cases began decreasing, their colleagues started reuniting with their children. Meanwhile, Weir and Yang said they sat together in their living room, longing to hear the clanking of kids' toys.

FIRST WORD, 'CHEESE'

Carmichael did the best she could to help, taking more than 1,000 pictures and 100 videos of Ainsley and Adeline. She said she wanted her sister and brother-in-law to feel as if they weren't missing a moment. But they were, especially with Adeline. One day, while posing for the camera, she spoke her first word: "Cheese."

"Adeline was barely walking" when she arrived, Carmichael said. "But now she runs around and confidently climbs onto the dining room table. You turn around for two seconds and it's like, 'Ah!'"

The videos, pictures and FaceTime conversations helped Yang and Weir endure the pandemic's peak, but by May they agonised over missing Adeline's first teeth or Ainsley's pronouncing certain words correctly. Swimsuit was no longer "swim-soup."

Each week, they mailed care packages to Singapore filled with toys and clothes they had ordered online or any "Frozen" merchandise they could find at CVS or Duane Reade. The packages were directed at Ainsley, described by her parents as a "precocious girl" whose emotions alternated between anger towards them, fear that they would die and sadness over not being near them. The child's swings could make video-chats painful, Yang said.

"One time, we sent her a package, and she asked, 'When is it going to get here?'" Yang said. "I accidentally went, 'The package is on an airplane and soon the mailman will deliver it to your house.' She immediately replied, 'This is not my house! This is Auntie Heather's house!'"

That was it. Ainsley's response pushed the couple towards a breaking point. While Weir covered a shift for someone at the hospital on Mother's Day, Yang sat on their couch for much of the day and scrolled through pictures of the girls, fantasising about holding a sleeping Adeline, the warmth of her head on her shoulder.

The simple act of walking in his front door became painful for Weir. Before the pandemic, Ainsley would welcome his return by opening it for him. Being outdoors tormented them, too. As the weather got warmer, Weir said he noticed people with children everywhere he went, making the void in his life bigger. Hearing babies cry in public gave Yang "a twist in my heart."

Singapore's borders remained closed, and its government wasn't helping. After Yang and Weir were denied visas, they learned the city-state would allow transit travellers beginning in June, but only from New Zealand and Australia. The couple launched a full-court press, appealing their denied visa applications and contacting the US Embassy in Singapore, the Civil Aviation Authority of Singapore, and the Immigration and Checkpoints Authority of Singapore.

"We went around and around," Weir said. "Someone at the Aviation Authority was like, 'Try calling Immigration.' We'd wake up in the middle of the night and call Singapore Immigration and they'd say, 'Call the Ministry of Health.' We'd call the Ministry of Health and they'd say, 'Call the Aviation Authority'."

Once they realised getting the girls back wasn't going to be easy, the regret set in. But whenever one of them second-guessed their decision, the other described what working at their respective hospitals was like a few weeks earlier. "There was a lot of back and forth," Weir said. "But we really didn't think it was going to be as bad as it was in New York. And then it got so bad. There's no way we could have functioned" with the girls.

Like most countries, Singapore continues to block American tourists from entering. It has since opened its borders to Chinese travellers, with other neighbouring countries to follow in August. All must wear electronic bracelets. Finally, six weeks after being denied entry, Yang and Weir were granted visas to Singapore on the condition that they quarantine in a hotel for two weeks upon landing.

The couple agreed, and on July 5, after 109 days without their children, they entered Carmichael's home, overcome with emotion. Ainsley gasped and screamed, ran and jumped into her mother's arms. Weir approached Adeline, but the one-year-old backed away.

"She didn't remember us at first, which was tough," he said. "But she warmed up quickly."

Over the next few days, whenever the girls slept, Weir and Yang watched over them and whispered about how lucky they are.

"This made us a stronger couple," Weir said.

As Covid-19 cases surge throughout most of the country, Yang and Weir said they are discussing what they will do if New York City becomes a hot spot again. Their potential plans do not include flying the girls back to Singapore.

"We can't live our life away from the kids again," Yang said. "We have to find a new way to make this work."