SINGAPORE — Two hours. That’s all the time medical teams in Singapore are given to uncover the first details of how patients contracted the coronavirus and which people they might infect.

Did they travel abroad? Do they have a link to one of the five clusters of contagion identified across the city-state? Did they cough on someone in the street? Who are their friends and family, their drinking buddies and partners in prayer?

As Western nations struggle with the wildfire spread of the coronavirus, Singapore’s strategy, of moving rapidly to track down and test suspected cases, provides a model for keeping the epidemic at bay, even if it can’t completely stamp out infections.

[Update: India, day 1: World’s largest lockdown begins.]

With detailed detective work, the government’s contact tracers found, among others, a group of avid singers who warbled and expelled respiratory droplets together, spreading the virus to their families and then to a gym and a church — forming the largest concentration of cases in Singapore.