“There have been chains of transmission in the community which have not been cut off. There might be more people going out, especially during weekends and holidays, and more gatherings,” said Dr Chuang Shuk-kwan, head of the communicable disease branch at the Centre for Health Protection.

“Those who have not been infected or those who have been hiding at home might have also gone out to hang out with others, which might lead to some transmissions.”

A cluster at Po Leung Kuk Lam Man Chan English Primary School in To Kwa Wan grew by seven cases, bringing the total to 14.

Chuang said more cases were being detected in schools because pupils and teachers underwent daily virus tests.

“There are nearly 1 million [students and staff] in total, so even with tens of cases or 100 cases, the proportion is similar to that of the community,” she said.

Outbreaks were also linked to more bars. The latest was Racks City nightclub in Central, where 18 patrons who had visited it between 9pm on June 4 and 2am the following morning were infected. Sheung Wan nightclub FLM was linked to a new cluster involving 13 infected customers who visited between 11pm on the same day and 2am.

Five more cases were added to a cluster linked to Shuffle bar in Central, bringing the number of infections to 118.

Society, meanwhile, has hotly debated whether trying to resume quarantine-free travel with the mainland should take priority over opening up fully to international travellers.

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Lam, who steps down in three weeks at the end of her five-year term, expressed fears about the city’s status.

“If Hong Kong cannot resume international travel, I worry that Hong Kong’s status of being an international metropolis or international financial hub will be affected because Hong Kong needs international interaction on cultural arts and innovation but it also needs to stay connected with mainland China,” Lam said in a radio interview.

She also noted that due to vaccine hesitancy among the elderly, their inoculation rate had remained low during the pandemic’s fifth wave, resulting in a large number of severe infections and overloading of public hospitals in the past few months.

Lam earlier ruled out a full reopening of the border with the mainland soon, stressing the city was caught between the nation’s stringent approach to stamping out Covid-19 and the rest of the world’s more flexible attitude of living with the virus.

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Incoming leader John Lee Ka-chiu, who takes over as chief executive on July 1, had stressed in his election campaign that quarantine-free travel with the mainland would be his top priority.

Government adviser Professor David Hui Shu-cheong, a respiratory expert from Chinese University, said the city’s reasonably high vaccination rates and a significant decrease in coronavirus-related deaths and critical cases could allow the financial hub to reopen to foreign arrivals.

“[Covid-19 restrictions could be further eased] if the city’s top priority is to reopen the border with foreign countries, as many others have been shortening quarantine and allowing home isolation,” Hui told a radio programme.

“But if the top priority is to reopen the border with the mainland, you can’t relax too much on gatekeeping as guarding against imported cases is part of the ‘dynamic zero-Covid’ approach.”

Hui said he expected the next administration to renegotiate with the National Health Commission soon on the latest priorities and criteria for reopening the border.

“Back in September last year, the mainland had not experienced the Omicron wave, but now many cities and provinces have dealt with such cases,” Hui noted, referring to drawn-out attempts last year at border reopening. He said officials from both sides needed to discuss whether Beijing had “changed its views”.

Recalling the previous rounds of talks, Hui said mainland authorities had expressed worry about potential infection clusters in Hong Kong’s quarantine hotels, and they had also argued that the discharge criteria for Covid-19 patients in local hospitals were too loose.

Hui urged Lee’s government to strike a balance between allowing residents who had families and businesses on the mainland to cross the border with ease and facilitating travel to the city for foreign investors.

He said that if the mainland was still bent on its “dynamic-zero” Covid-19 policy, authorities could consider a “closed-loop” mechanism to resume quarantine-free travel across the border for designated groups.

Since May 1, international travellers have been able to fly into the city but they must serve seven days in hotel quarantine. They also need to undergo multiple virus tests during and after their isolation.

Hong Kong leader rules out reopening border with mainland China any time soon

Hui said the increase in caseloads was not surprising given the easing of social-distancing rules.

“[Restaurants] have longer working hours and bars are reopened, the recent increase in the number of cases is within expectations,” he said, adding that the return of overseas residents also brought more cases to Hong Kong.

He urged people not to be too worried, considering there were much fewer coronavirus-linked deaths and severe cases, as well as an immunity barrier as half the population had been infected in the fifth wave.

Citing recent research, Hui said vaccination was still effective in preventing severe cases and deaths caused by Omicron subvariants.

But he warned it was not the right time to further ease social-distancing curbs and arrival quarantine arrangements, with the city set for a series of celebrations to mark the 25th anniversary of its return to Chinese rule.

The city’s overall tally stands at 1,218,365 cases with 9,390 related fatalities.