“Before the epidemic worsens, the government should step up inspections of high-risk places, such as restaurants and bars. If relevant places have not abided by the rules, immediate prosecutions should be made.”

But Dr Chuang Shuk-kwan, head of the communicable disease branch of the Centre for Health Protection, said the city’s third wave of infections “was not over yet” when asked about Ho’s statement at a regular press conference. She did not elaborate further.

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Among Monday’s infections was an 18-year-old student at the Youth College in Tuen Mun. The student was one of eight people at a September 27 gathering at the Gateway Hotel in Tsim Sha Tsui attended by two people previously confirmed to be infected. Both were linked to the China Secret bar cluster. The other five were to be placed in quarantine.

Chuang said because the student had attended school during her transmission period, the college would need to temporarily close and specimen bottles would be delivered there for testing.

She said the Tuen Mun campus of the Institute for Vocational Education, which sits directly next to the college and shares some of the same facilities, would also be closed and given bottles for samples.

A spokeswoman for the Vocational Training Council, which operates the two schools, said the campuses would be closed until October 19, marking two weeks from the student’s last visit to the campus. Two students considered close contacts of the infected girl had already been sent to quarantine, she added.

Monday’s sole case without a traceable source, meanwhile, was a Pakistani woman who returned to the city in July and currently lives in So Uk Estate in Cheung Sha Wan. She had undergone mandatory quarantine upon arrival and twice tested negative for the virus.

Her infection was only discovered during a routine Covid-19 screening taken when she was admitted to a hospital on October 10 due to lower back pain.

While the woman’s source of infection was still unclear, Chuang did not rule out the possibility her case may have been imported.

“She might have been infected in Hong Kong, as she has been in the city for a while,” Chuang said. “But when she tested positive, she was already found with antibodies for the virus and her [viral load was low]. So we can’t say whether she was infected earlier and it just wasn’t detected when she arrived … or if she was infected in Hong Kong.”

She added that the woman’s husband and baby would be quarantined and tested.

The six imported infections involved arrivals from Germany, France, Britain, Switzerland and India. The city’s overall tally now stands at 5,193 infections, with 105 related deaths.

Ho, the HKU professor, said he believed the government should be identifying more high-risk groups for testing, as well as increasing the number of locations for distributing and collecting test sample bottles, and extending service hours.

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A day before, Professor Yuen Kwok-yung, an expert from HKU advising the government on the pandemic, suggested mandatory testing should be done on those displaying symptoms associated with the coronavirus, but family doctors were sceptical.

Henry Yeung Chiu-fat, president of the Hong Kong Doctors Union, said it was not feasible to force patients who were voluntarily seeing a doctor to undergo testing.

Dr Cheng Chi-man, a family doctor and vice-chairman of Hong Kong’s Medical Association, agreed it would be difficult to implement.

“[It could be done] only if there is a law enforcement agency involved. Usually there are only a doctor and two nurses at a clinic, how can a test be forced on a patient?”

But Executive Council member Dr Lam Ching-choi said he believed mandatory testing could be done for the sake of public health, given that Covid-19 patients were more likely to be found among people with symptoms rather than groups considered high-risk such as taxi drivers or care home workers.

According to existing prevention and disease control regulations, a health officer can require a person suspected of suffering from an infectious disease to undergo a test. Lam said the law could be amended to grant all registered doctors in Hong Kong that authority.

The government in August also amended the law to authorise public officers outside the health establishment to help conduct contact tracing.

Meanwhile, Princess Margaret Hospital made an apology on Monday after 10 saliva specimens submitted for Covid-19 testing at its outpatient clinic on Saturday were not sent to the laboratory the same day as usual, meaning those involved would have to resubmit their saliva or nasal swab samples.