The highs and lows in life today for Dr Vernon Lee, 42, are tied closely to whether his team is able to find the source of coronavirus infection in patients who caught the disease locally.
As he is the director of communicable diseases at the Ministry of Health (MOH), it is his team that has to identify - and serve quarantine notices to - all close contacts of someone who is infected. They aim to do all this within 24 hours, to minimise spread of the virus.
The first cases were all visitors from Wuhan whose contacts were fairly limited. Although the visitors went sightseeing, they would only have had brief contact with people here, and so had little danger of spreading the virus to them.
The difficulty came when local cases with no known sources emerged.
Dr Lee says: "The most challenging part is to incorporate the many streams of information coming from various sources, and to piece together the picture of how the Covid-19 cases could have been infected."
It can be frustrating when faced with new cases for which it is difficult to find links.
But his team managed to trace some - they discovered that three people here had most likely contracted the infection at The Life Church and Missions, which a couple from Wuhan had attended. The China couple were confirmed to have the coronavirus infection.
"The most rewarding is when we are able to find a link, and when our contact tracing and containment measures are able to prevent further spread from the particular case," says Dr Lee.
That, and encouraging messages from friends and even mere acquaintances "has warmed my heart and gives me strength to carry on the fight", he said.
He had been all set to go on a holiday to Bangkok with his family over the Chinese New Year long weekend when Singapore reported its first coronavirus case, a visitor from Wuhan.
He recalls: "My family was very understanding. I told them to carry on with their trip, as my work shouldn't affect their plans. But I had to miss the reunion dinner and precious time with my family."
Dr Lee has been involved in epidemiological investigations for the severe acute respiratory syndrome (Sars), as well as bird flu in Indonesia when he was seconded by the MOH to the World Health Organisation to help with the outbreak there.
He has also worked on the swine flu and Zika outbreaks.
"A lot of the investigation work requires experience to have a feel of where and what to investigate to maximise success," he says.
But he says his work is made more difficult by rumours and misinformation spread on social media: "That undermines the real information that we are putting out. Addressing this misinformation takes time and draws us away from the important work."