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Block 11 of Carmel Cove was locked down at 7pm. Photo: Felix Wong

Coronavirus: quarantine for hundreds after Hong Kong records first untraceable local case involving Covid-19 mutated strain, health officials warn of ‘grim situation’

  • The patient, a domestic helper, has not travelled outside the city since arriving in 2019, health officials say
  • Authorities cordoned off Block 11 of Carmel Cove at Caribbean Coast housing estate at 7pm for overnight testing of residents
Hundreds of occupants of a 52-storey residential block in Tung Chung have been ordered into quarantine in Hong Kong’s biggest such operation after one of them was confirmed to have contracted a mutated strain of Covid-19 from an unknown source locally for the first time in the city.

Authorities cordoned off Tower 11 of Carmel Cove at the Caribbean Coast housing estate at 7pm on Thursday for a lockdown exercise expected to end at around 7am on Friday after testing of all residents was completed. Occupants will have to undergo three weeks of quarantine in government centres.

Health officials said the patient was a 39-year-old domestic helper from the Philippines, and her infection carried the N501Y and E484K mutations. Both types were found in more infectious strains first identified in South Africa and Brazil, and further sequencing would be needed to determine the variant.    

The woman had not travelled outside the city since arriving in 2019, Dr Ronald Lam Man-kin, controller of the Centre for Health Protection, said, raising fears of the strain already spreading in the community.

Her employer’s 10-month-old daughter had also tested positive and genetic analysis was being carried out to see which strain she had.

“For this case, we have not been able to trace the source. … As it is the first locally contracted case involving a variant and one of the family members was also infected, we think the situation is very grim,” Lam said.

“Including the latest case, there have been four cases involving a coronavirus variant detected in the community. She developed symptoms on April 23. During the 14-day incubation period, she had been in Hong Kong.

“There is reason to believe this is the first local infection with no traceable source. So we take it very serious and will handle it very carefully.”

Residents of Block 11 are tested at a mobile screening centre at Carmel Cove. Photo: Felix Wong

More clues were available in the three previous cases involving variants because two of the patients had a recent history of travel and the other was a close contact.

“There is no sign the [four] cases had epidemiological links. But it still remains to be seen if more clues will emerge with our further investigation, including tracing and testing. In the meantime, it is still an untraceable local case,” Lam said.

The helper had visited five places during the incubation period, including St Thomas the Apostle Church in Tsing Yi on April 11 and 18, Fu Tung Plaza in Tung Chung between April 9 and 29 and the nearby Citygate Outlets on April 25. She was in Man Tung Road Park near her home on April 11, 18 and 25, and at a Fusion supermarket in Caribbean Coast on April 12 and 16. 

Lam said those who visited the same places on the same dates would be subject to mandatory testing. More than 10 fellow choir members of her church had already been tracked down, he said. 

The first batch of residents from the block’s 400-plus flats were sent to quarantine centres shortly before midnight on Thursday. The government has 2,951 units available for immediate use for asymptomatic close contacts of confirmed patients. Some units can house more than one person. 

Dr Albert Au, principal medical and health officer, said those issued with mandatory testing orders would also have to get screened on the first, seventh, 14th, and 21st day of isolation.

Earlier in the day, a researcher revealed to the Post that the third local variant case, also a domestic helper, did not contract the virus from neighbouring guests in her quarantine hotel as initially suspected.

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Genome sequencing conducted by Polytechnic University found that the 38-year-old Filipino, who was confirmed to be carrying the N501Y mutation last Friday, had a different variant than the family in the opposite room at the Ramada Hong Kong Harbour View hotel in Sai Ying Pun

The helper, who stayed at the hotel earlier this month, was found to be carrying the South African variant known as B. 1.351.

But of the three infected family members across the hall, two are known to have been infected with the variant first identified in Britain: B.1.1.7. The viral load of the third person was too low to determine which variant they carried.

“Based on the whole genome-sequencing result, the family could not be the source of the [domestic worker’s infection],” said Dr Gilman Siu Kit-hang, an associate professor from PolyU’s health, technology and informatics department who led the research.

“We are sorting out other cases who stayed in the same hotel over the same period.”

He said other possibilities could explain the helper’s infection. 

“Perhaps she already got the virus before arriving in Hong Kong but her infection was not detected [during quarantine] due to sampling issues,” Siu said. “She could also get infected by other cases in the hotel.”

Singapore sees highest local cases in months; Philippines extends lockdown 

He said the latest findings suggested the helper was not infected by her neighbours through airborne transmission, as experts had believed. “The transmission might have happened when she used the lift or through other items,” Siu said. 

Hong Kong recorded 15 new Covid-19 cases on Thursday, all of which were imported. Thirteen of those cases were arrivals from Nepal, and the remaining two from Indonesia and India. Two of the infections from Nepal were found to carry the N501Y mutation. 

Hong Kong’s tally of confirmed infections now stands at 11,770, with 209 related deaths.

04:06

International community races to help India tackle worsening Covid-19 outbreak

International community races to help India tackle worsening Covid-19 outbreak

Meanwhile, the government announced a ban on all passenger flights from Nepal from Saturday, and extended existing ones on India, Pakistan and the Philippines. People who have been in these countries for more than two hours will also be barred from entering Hong Kong.

The bans were imposed through a mechanism under which flights will be suspended for 14 days if five or more cases involving the N501Y mutation are detected among passengers from the same country in a seven-day period.

The government also tightened the rule on Thursday, saying all other relevant mutations that could potentially pose similar risks to Hong Kong’s public health would also be considered.

The new rules will also see the triggering of the suspension mechanism if seven or more N501Y or related mutant strain cases are detected among passengers when they arrive or during their quarantine in a 10-day period.

A review would then be conducted every two weeks to see if any bans imposed should be lifted.

Nepal has experienced a surge in daily Covid-19 infections, from around 500 cases two weeks ago to more than 4,500 on Wednesday.

University of Hong Kong infectious disease expert Dr Ho Pak-leung said the government should consider designating Nepal an “extremely high-risk” country.

In Hong Kong, Thursday also marked the resumption of business at some bars, party rooms, saunas, karaoke lounges, mahjong and Tin Kau parlours as well as a loosening of social-distancing measures governing restaurants and gatherings such as weddings and religious events.

The new multi-tiered “vaccine bubble” represents an attempt to boost the city’s sluggish inoculation campaign as well as a potential boon for the bars and restaurants, though numerous voices in the sector have complained about the complexity of the new measures.

As of Thursday, 897,120 people – or 12 per cent of residents – had taken their first vaccine jab in Hong Kong, while 480,523 had received both doses.

Additional reporting by Rachel Yeo

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