One of the returnees confirmed as infected was a 34-year-old man living in Pakistan with his parents, while the other was a 16-year-old female student from Hong Kong who travelled to the South Asian country to visit family on March 3.

With no new local infections recorded since April 22, Dr Chuang Shuk-kwan, head of the Centre for Health Protection’s communicable diseases branch, pleaded with the public to remain both vigilant and patient.

“It is expected that there will be more imported cases in Hong Kong, and we hope the virus will not be transmitted to the community,” she told a press briefing.

“The incubation period can be as long as 14 days, and for some of the cases it may be longer. Therefore it’s very difficult to say it is all under control at the moment.

“Although we have seen the infection figures drop significantly, we cannot be very confident that the local outbreak is over, or transmission has stopped, as we have to wait for some time.”

Pandemic drives rethink of Hong Kong’s hospital needs: authority chief

Indicating May 20 as a potential date when Hong Kong could declare victory over Covid-19’s community spread, Chuang said: “The last local case was sent to hospital on April 22, so if there are no new cases in two incubation cycles [of 28 days], we can say the local outbreak is under control.”

She added that she understood people might want to head outdoors during the public holidays, but reminded them to stay vigilant. It was also revealed on Friday that 13 more coronavirus patients had been discharged from hospital.

On arrival in Hong Kong, all of the returnees from Pakistan had their saliva tested for the coronavirus at the AsiaWorld-Expo complex, near the airport.

According to the Immigration Department, 2,000 city residents were trying to leave Pakistan, while another 3,200 were stranded in India.

Hong Kong has been in a state of public health emergency since January 25, four days after reporting its first imported case.

Chuang said the status would likely remain in force for the foreseeable future to tie in with the World Health Organisation’s global pandemic declaration, which was announced on March 11.

Meanwhile, the government said in a Facebook post that, since February, four people had been jailed for violating quarantine, while another 56 were under investigation over alleged breaches.

More than 14,000 spot checks for home-quarantine compliance were carried out, which accounts for 9 per cent of all arrivals from mainland China and overseas. More than 75,000 wristbands were issued over that period.

As the city marked 100 days since its first coronavirus cases, Chuang said Hongkongers were comparatively more vigilant than others, adding that was probably down to the city’s battle with the severe acute respiratory syndrome (Sars) in 2003.

“We have an efficient flow of information, people’s reactions have been quick and members of the general public are patient enough. It’s the ultimate effort and testament to the hard work of all people in the city,” she said.

Dr Linda Yu Wai-ling, the Hospital Authority’s chief manager of clinical effectiveness and technology management, said the authority had gone through ups and downs in the past few months, referring to a period when there were insufficient isolation wards and supplies of protective equipment.

“We are lucky to have a group of sedulous frontline staff and cooperative citizens that stick with social-distancing measures,” she said. “We hope we will continue these efforts, so that we can win this war together.”

With the city’s infected tally remaining relatively static, the government has been under pressure to relax border control and social-distancing measures, although Chief Executive Carrie Lam Cheng Yuet-ngor has said that should come gradually.