They included postponing university entrance exams by a month and ordering civil servants to resume working from home, starting on Monday.

At a regular press briefing on Sunday, Dr Chuang Shuk-kwan, head of the communicable disease branch of the Centre for Health Protection, said seven of the new cases were students who returned from overseas study. Four of them were studying in Britain before they returned.

Mount Kelly international school, which had earlier arranged a tour to Switzerland, recorded at least two new cases, bringing the total to six including two staff and their close contacts. Seven students who joined the tour have not shown any symptoms of Covid-19 and have passed the 14-day incubation period.

“Obviously there are a lot more imported cases, it’s hard to predict how many more cases we will have in the coming few days,” Chuang said. “We hope after the enhanced measures, they will remain in home quarantine and there will be fewer close contacts afterwards.”

Two more people who visited Canada and Bolivia on a tour were also confirmed with the infection, taking the total number of cases in the group to seven.

Chuang said a handful of confirmed cases had travelled to or previously studied in Britain, but stopped short of saying whether travellers from there tended to be more risky.

While Singapore and Taiwan had starting banning transiting through their airports, Chuang shrugged off the idea for Hong Kong, saying only one case involved a tourist visiting the city.

“Most cases confirmed so far involved Hong Kong residents coming back to Hong Kong,” Chuang said.

She said the quarantine measures could reduce the risk of a community outbreak.

On local cases, the youngest confirmed case was a 20-month-old girl. The child was among a group who attended a wedding on March 14 in Discovery Bay. The toddler’s parents and the groom were infected earlier. There have now been eight confirmed cases involving the wedding group.

Coronavirus latest: Singapore shuts border to visitors; Malaysia deploys troops

Four cases involved people who had been to the entertainment hubs of Lan Kwai Fong and SoHo in Central, including a band member who performed in several bars.

Chuang reiterated that there was no proof Lan Kwai Fong was a particularly risky area that warranted a complete shutdown.

“It’s not about a particular place,” she said. “If one place is closed, people will go to another place, it’s about a change in attitude, and we all need to reduce social interaction.”

Sunday’s cases were the second-highest daily tally recorded since testing began in the city. The highest came last Friday, with 48 new coronavirus infections.

Meanwhile, the Hospital Authority confirmed it was in talks with the government to build more temporary isolation wards. No further details were immediately disclosed.

“We will cooperate with the government, and see how long it will take to build these facilities,” said Dr Linda Yu Wai-ling, a chief manager with the authority.

About 400 general wards with negative pressure capacity – designed to prevent germs from spreading – across all public hospitals would be turned into isolation wards later in March, in the face of the influx of travellers.

Yu also confirmed that patients recovering from Covid-19 would be transferred to these new wards, since standard isolation wards were in high demand.

“We will use these wards to host those patients who already have been treated and are in stable condition,” Yu said, adding staff treating them would wear full protective gear.

Dr Tony Ko Pat-sing, chief executive of the authority, also confirmed the new arrangements on his official blog, saying it was a new strategy to cope with the increasing number of cases, as the authority was “very concerned that the isolation facilities will soon be overloaded”.

He added: “The authority will expand its containment strategy targeted to cut off imported cases, including strengthening tests for travellers and increase the capability of isolation wards in receiving cases.”