Despite limits on social gatherings, mass testing and mandatory mask wearing, Hong Kong has detected a handful of Covid-19 infections from unknown sources every day over the past week. A top expert has told HKFP that “leakage” in the quarantine system due to premature testing of incoming travellers and lax hotel quarantine measures may be to blame.

Respiratory infectious disease expert Dr Leung Chi-Chiu warned that the government has just a few weeks to stem local transmissions before temperatures drop in December and people become more prone to respiratory infections.

Dr Leung Chi-Chiu
Dr Leung Chi-Chiu. Photo: CGTN screenshot.

“Whether we can eliminate local transmissions and whether we can guard against imported cases in the coming winter, these are crucial issues,” said Leung, a former chairman of the advisory committee on communicable diseases at the Hong Kong Medical Association.

The city recorded eight confirmed cases on Tuesday, two of them from unknown sources.

4th wave?

Hong Kong has suffered three waves of infections in all. The first started in late January, linked to travellers from the mainland as the Chinese government began to grapple with the disease within its borders. The second wave in March was linked to travellers returning from Europe and the US. And the third wave in July was connected to travellers who were exempted from quarantine, including seafarers and air crew.

File Photo: May James/HKFP.

“The genetic lineage of the virus in each wave in Hong Kong has been different, and each one was triggered by imported cases,” Leung said, “There are still quite a lot of loopholes in our quarantine arrangements.”

After an initial Covid-19 test at the port of arrival, Hong Kong health authorities currently test travellers a second time on the 10th day of their quarantine period, instead of on the 14th day when the quarantine period ends. “That means we would be missing about ten per cent of the cases under incubation,” Leung said.

While the median Covid incubation period is five to six days, in one in ten cases the onset of infection takes longer than ten days, Leung said. So testing on day ten may miss potential cases.

covid covid-19 coronavirus face masks mtr
Photo: Kaiser/HKFP.

The government initially was short of testing capacity so opted to conduct tests a few days before the end of quarantine in order to avoid delays in receiving results. Leung warned that – with a global rebound expected – this practice could exacerbate “leaks” from imported cases.

Cross-transmission is a second major risk, he said, because Hong Kong does not currently have hotels designated uniquely for quarantining incoming travellers. The businesses are allowed to receive other guests. Travellers who quarantine at home may also mingle with others in the family. Recent hotel outbreaks – such as that at the Royal Garden – are “clear warning signals,” Leung said.

“In Hong Kong, mainly we did relatively well after all the previous waves,” said Leung. “But the continuous ‘leakage’ may have been the key factor in occasional local outbreaks.”

Hong Kong has reported 5,201 coronavirus cases this year and 105 deaths.

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Selina Cheng is a Hong Kong journalist who previously worked with HK01, Quartz and AFP Beijing. She also covered the Umbrella Movement for AP and reported for a newspaper in France. Selina has studied investigative reporting at the Columbia Journalism School.