An unknown number flashed up on the phone of Kylie Davies-Worley, a retail consultant who has lived in Hong Kong for almost 20 years, at 8.30am on Saturday morning. Her 18-month-old son had been exposed to coronavirus at a playgroup, the caller said. A bus would arrive in the next 24 hours to take them to a government quarantine camp where they would be detained for the next 14 nights.

“At that point we hit panic stations,” Davies-Worley said. Their experience was mirrored by hundreds of families across Hong Kong last week, sparking a debate among the expat community over the trade-off between civil liberties and controlling Covid-19.

For many expats, it marked the first time they have been confronted with the harsh reality of the battle against coronavirus in Hong Kong, where cases have been far lower than in their home countries. “We get that it is necessary, but the three of us locked in this tiny room is not a good setup for babies,” said Davies-Worley’s husband Nick, an executive at consulting group Bain, from a quarantine camp near Hong Kong’s Disneyland resort.

“It’s heartbreaking. Our son keeps hitting the door saying ‘out, out’,” Ms Davies-Worley added. About 860 people were quarantined last week following an outbreak at Ursus Fitness, a gym popular with expats.

It has grown into the second-largest cluster of cases in Hong Kong since the start of the pandemic, spreading rapidly through the city’s expat and financial community.