As a consultant emergency physician at National University Hospital, Dr Ong Pei Yuin has had to tend to potential Covid-19 patients.

The 42-year-old strives to calm and reassure them as she tests them for the disease.

She understands their emotional turbulence: She herself was a Sars patient.

When Covid-19 hit Singapore in January, she felt a dreaded sense of deja vu. "Oh, it was like Sars all over again. I don't want to go through it all over again."

In 2003, she contracted the severe acute respiratory syndrome (Sars), never felt sicker in her life and was warded for 14 days in hospital.

She was 26 then, a first-year medical officer at Tan Tock Seng Hospital, the designated hospital to treat Sars patients.

She was also a bride-to-be.

It started with a high fever that refused to break. And she almost blacked out one morning after getting out of bed.

She remembers the unremitting fever, the chills and the body aches. She also came down with pneumonia. "It was the worst illness I have had," she said.

The physical suffering aside, the isolation she experienced when she was warded was also hard to bear.

Her parents and two brothers were quarantined at home and she was not allowed visitors.

But calls from loved ones and prayers helped her through that dark period.

"A lot of people rang and asked how I was. Their words of encouragement helped. Some family and friends dropped off food," she said. "These little things helped."

She felt very grateful to survive Sars without suffering any lasting complications, for she had colleagues who died.

A total of 238 people were infected with Sars here and 33 died.

Nine months after her illness, Dr Ong tied the knot with her boyfriend from medical school. She suffered some hair loss during the Sars treatment, but they grew back in time for the wedding.

Her husband is a paediatrician and they now have two children, aged 10 and 14.

When Covid-19 struck, the initial days of grappling with yet another unknown virus was "a bit challenging", she said.

Dr Ong, who has tested at least one Covid-19 patient, said: "I reminded myself this is what we are called to do. We are trained to do this. The time that we have prepared for is here now."

She said Singapore's Sars experience has helped the country to better tackle the current crisis, for example, in ramping up the number of isolation beds, among other measures. When she was infected with Sars, she was warded in a four-bed ward due to the lack of isolation rooms then.

And everyone, from the healthcare system to the public, has a role to play in keeping front-liners like healthcare staff safe, she said.

Dr Ong knows from experience it is important to care for oneself to prevent burnout. She swims and cycles to de-stress.

She said: "Not knowing how long the journey is something quite difficult. We need to pace ourselves as it might be a very, very long marathon."