Hong Kong health authorities have established a transmission link among five people with a mutated strain of Covid-19 in a breakthrough that may ease concerns about the community spread of more infectious variants, but uncertainties remain over how much of a continuing risk the city is facing.
Extensive contact-tracing results on Wednesday showed that three variant cases involving foreign domestic helpers – the latest two at the Kornhill and Royalton private housing estates in Quarry Bay and Pok Fu Lam, alongside an earlier case at the Caribbean Coast in Tung Chung – had partied together with a woman from the Philippines working in a clinic and her brother in Sham Shui Po, according to a source.
The situation seems less worrying, but we cannot be too careful as the chain of infection may not end yet
Dr Joseph Tsang
The woman and an engineer from Dubai, whom she was friends with, earlier became the first two cases of variant infections discovered locally.
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The source said on Wednesday that the pair had been uncooperative all along in providing details of their movements and whereabouts.
It also emerged that the woman had paid a visit to her mother’s home at a public housing estate in Chai Wan, and both the mother and brother had been sent to hospital to wait for test results.
The two infected domestic helpers from the Philippines carried both the N501Y and E484K mutations, found in variants from either Brazil or South Africa. Health authorities had previously confirmed that the engineer and his friend carried the variant from South Africa.
Authorities have detected 10 variant cases in the community so far, seven of which have been identified as local infections.
After mandatory testing orders were issued last Friday to all 370,000 foreign domestic workers in the city, three were found to be infected with mutated strains, raising concerns that it could signal the spread of variants in their community.
The two carrying the N501Y and E484K mutations had no recent travel history, and their cases prompted authorities on Tuesday night to order the quarantine of hundreds of residents from two affected blocks in Quarry Bay and Pok Fu Lam.
The third domestic worker, living in Tsuen Wan, was found to be infected with the N501Y mutation only a month after she arrived from the Philippines. Her case has been categorised as a potential local infection from an unknown source.
The N501Y mutation has health officials particularly worried, as it has been linked to more transmissible variants, including those first identified in Britain, South Africa and Brazil.
The Centre for Health Protection said on Wednesday that the engineer from Dubai and his friend had attended a family gathering with the woman’s relatives on April 13 at Fung Hing House of Hing Wah II Estate in Chai Wan.
“Subsequently, three of the attendees of that gathering had another gathering at their home at 37 Fuk Wing Street in Sham Shui Po … on April 18,” the centre said in a statement.
“In accordance with the latest information, the [centre] has immediately arranged attendees of both gatherings to undergo compulsory quarantine.”
Those who visited two eateries in Central where two attendees of one of the gatherings worked at – Urban Bakery Works at the Landmark Atrium and Oliver’s Delicatessen at Landmark Prince’s – have also been ordered to undergo testing by Friday.
Hong Kong confirmed six new infections on Wednesday, three of them imported cases from Nepal. The city’s Covid-19 total now stands at 11,796 cases, with 210 related deaths.
Infectious disease specialist Dr Joseph Tsang Kay-yan welcomed the identification of the transmission links among the variant cases.
“The situation seems less worrying, but we cannot be too careful as the chain of infection may not end yet,” he said. “It takes time to do tracing and people should be cooperative, they should try not to hold back anything. It does no good to anyone.”
Another infectious disease expert, Dr Leung Chi-chiu, said both the domestic worker in Tsuen Wan and a housewife from India confirmed to be carrying the N501Y mutation were likely to have been infected before arriving in Hong Kong.
“They both already carried antibodies for the coronavirus, which suggests they could have been sick for more than a week,” Leung said. “As their viral load was also very low, it’s likely they had already been sick and were recovering, and retested positive from the remaining traces of the virus.”
Their infections were not picked up at the airport because Hong Kong did not test for antibodies upon arrival, he explained, adding the patients were unlikely to be highly infectious as their viral load had not increased.
Leung said there would be more such cases if the city did not ban travel from all high-risk countries, and warned that it would be dangerous for the government to reduce the quarantine period for vaccinated travellers.
There was no scientific basis for shortening quarantine, as no vaccine could reduce the coronavirus’ incubation period, he said.
Executive councillor Dr Lam Ching-choi, a member of Chief Executive Carrie Lam Cheng Yuet-ngor’s de facto cabinet, said the city could not afford to let its guard down.
“So far, three cases is still a small figure and it seems there is no community transmission, thus the situation is still manageable and controllable,” he said. “However, if more helpers are confirmed to be infected by May 9 when the compulsory testing is finished, with sporadic cases spreading around the community, then there could be another major outbreak.”
In a related development, Secretary for the Civil Service Patrick Nip Tak-kuen, who oversees the city’s vaccination programme, said in a Facebook post that the number of people who had received their first dose had surpassed the 1-million mark as the roll-out entered the 69th day on Wednesday.
A total of 1,593,570 doses of Covid-19 vaccines have been administered as of Wednesday – 1,005,425 people, or 13.4 per cent of the population, have received their first shot, and 588,145 people, or 7.8 per cent, have taken their second dose.
Additional reporting by Lilian Cheng and Ng Kang-chung
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