Dhaka, Feb. 14 -- But the January sales meeting in a luxury Singapore hotel was far from auspicious.

Someone seated in the room, or in the vicinity of the hotel that is renowned for its central location and a racy nightclub in the basement, was about to take coronavirus global.

Three weeks later, global health authorities are still scrambling to work out who carried the disease into the mundane meeting of a firm selling gas meters, which then spread to five countries from South Korea to Spain, infecting over a dozen people.

Experts say finding this so-called "patient zero" is critical for tracing all those potentially exposed to infection and containing the outbreak, but as time passes, the harder it becomes.

"We do feel uncomfortable...