She said reducing the number of people in common areas and contact between workers was as important as maintaining good hygiene. So far, 65 confirmed cases were linked to Hong Kong’s biggest container terminal.

The Transport and Housing Bureau said a meeting was held between its officials, the Department of Health and terminal operators to follow up on measures to reduce the spread of the virus. The office and resting room of Wang Kee were disinfected and their use suspended.

Chuang also revealed that a 33-year-old man, who was confirmed to have Covid-19 in late March and recovered in April, was found to be carrying the virus after a trip to Spain via London this month. She said more investigations were needed to determine why he had the virus.

04:53

Jobless struggle to make ends meet in Hong Kong as city battles coronavirus and recession

Jobless struggle to make ends meet in Hong Kong as city battles coronavirus and recession

“We are not sure if he had been carrying the virus all this time, or whether it was a new infection,” Chuang said. “Covid-19 is still very new, our understanding of this virus evolves during the pandemic.”

Infectious disease specialist Dr Joseph Tsang Kay-yan said reinfection was more probable as it was unlikely traces of the virus would remain in the body for three to four months.

There could be a few reasons for reinfection, he said. “The patient’s antibody response is somehow waning. Another reason could be the patient had problems with his immune system. With weakened immunity, the patient’s antibody level might not be that high,” Tsang said.

The other possibility was the patient acquired a new strain of the virus. Tsang said reinfection of recovered Covid-19 patients had also been reported in the US and mainland China.

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Another domestic worker was also confirmed as infected. The 36-year-old Indonesian stayed at a dormitory in Cheung Hing Mansion, in Mong Kok, which was linked to recent cases.

“It has been over a month since the beginning of the third wave and the public is understandably starting to be fatigued by the social-distancing measures,” the Food and Health Bureau said. “However, it is not yet time for relaxation and there is no room for complacency in epidemic control.”

Although the daily number of new cases had eased from its peak in late July, it remained at a significant level with the seven-day average still beyond figures recorded at the height of the second wave in March and April, a spokesman added.

“The stubbornly high proportion of new cases with unknown sources of infection at some 40 per cent … indicates that silent or subclinical transmission chains are prevalent in the community,” he said. “It is highly worrying that such transmission chains persist despite extensive testing.”

The city has gone more than two weeks with fewer than 100 infectious per day. The total number of cases stands at 4,524, with 69 related deaths.

There were more than 20 preliminary positive cases. Among them was a man, 71, at Kwong Wah Hospital in Yau Ma Tei, who had been in the same ward as two infected patients. Hospital Authority chief manager Dr Lau Ka-hin said transmission could be linked to an uncooperative patient who often took off his mask.

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Another of the positive cases was linked to Wang Kee.

Despite calls to ease the evening dining ban, the government did not relax the measure, which prohibits dine-in services from 6pm to 5am. During the day, no more than two people can eat at the same table, and restaurants can only operate at half capacity.

Fourteen types of establishments, such as bars, gyms and sports facilities, will also remain closed for another week.

The arrangements were unveiled as the city prepared to launch mass Covid-19 screenings. But according to an email sent by the Food and Health Bureau to private doctors’ unions, the commencement of the scheme would be postponed to August 31, and last for two weeks.

04:16

Hong Kong reverses all-day restaurant ban, as city reports record high 149 Covid-19 cases

Hong Kong reverses all-day restaurant ban, as city reports record high 149 Covid-19 cases

The bureau said in the recruitment email that it aimed to set up swabbing stations in 18 districts to provide tests conducted by health care professionals, while supervisory posts at the stations should be held by registered doctors, dentists or nurses.

In another development, Professor Gabriel Leung, dean of the University of Hong Kong’s faculty of medicine who advises the government on its coronavirus response, said the transmission rate, which had shot up to between three and four earlier in the third wave, had started to rise again to about one, after dipping to around 0.5 three weeks ago.

Leung attributed the uptick to “anti-epidemic fatigue”, which he said could be shown in traffic data where Octopus card holders of all age groups had gone out more than in previous weeks.

“Now is definitely not the time to consider lifting any measures, we are at a critical stage and must hold our nerve for at least two more weeks,” Leung said.

Other medical experts were divided on whether the dining ban, which has been in place for more than a month, should be relaxed.

Public health experts Professor David Hui Shu-cheong and Dr Ho Pak-leung warned easing it could potentially lead to a resurgence in infections, but Medical Association president Dr Gabriel Choi Kin believed it could be “slightly relaxed”, as many restaurants were struggling financially.

Allan Zeman, chairman of Lan Kwai Fong Group, urged the government to review the policy.

“The food and beverage industry, bars and gyms are on the way to bankruptcy,” he said. “The government should make a right balance between the economy and public health.”

Separately, Lei Yue Mun Park and Holiday Village in Chai Wan – a community treatment facility for Covid-19 patients with mild symptoms – temporarily closed for renovation.

“We will install more Wi-fi and upgrade the electricity,” said the authority’s Lau, adding patients were transferred elsewhere.