Missing piece finally found in mutant strain puzzle

Top News | Jane Cheung 4 May 2021

Citygate mall in Tung Chung was the missing puzzle piece linking the transmission chain of the city's first two patients carrying the more infectious South African coronavirus variant to a helper - they had been to same mall on the same day, authorities said.

The Centre for Health Protection yesterday said contact tracing found the trio - a 29-year-old Indian man, his 31-year-old friend and a 39-year-old Filipino helper living in Tung Chung - had all been to the same mall on April 11.

That explained why genetic sequencing found the variant from the Indian man detected on April 16 and the helper - who had no travel history - were identical.

It indicated the same source of infection or one had passed the virus to another, but authorities could not establish how the transmission happened until yesterday.

The man and his friend had also eaten in the same restaurant - Curry Lounge in Seaview Crescent - on the same day.

Authorities have issued mandatory test notices to all visitors of the mall and the restaurant on April 11 to trace possible silent carriers.

Meanwhile, dozens of residents from Beauty Mansion on 71 Kimberly Road, Tsim Sha Tsui, were taken to Penny's Bay quarantine center last night, after a resident tested preliminary positive for the more infectious N501Y mutant strain.

The resident - a 28-year-old housewife - took Tata Sia Airlines' UK6395 flight from India to Hong Kong on April 4 and observed a 21-day quarantine at Regal Oriental Hotel before she returned to Beauty Mansion on April 25.

She was required to test again on her 26th day of arrival last Friday, but results were uncertain, prompting authorities to admit her to a hospital, where she eventually tested preliminary positive.

As a precautionary measure, residents in all 39 units of Beauty Mansion were sent to 21-day quarantine last night.

Earlier, government adviser Yuen Kwok-yung said authorities must check against loopholes at the airport, quarantine hotels and in testing processes or else there would be a fifth - or even sixth - wave of outbreaks.

The collection of samples in Hong Kong is much laxer than those in the mainland, he added, and improper sampling by test contractors may lead to false negative results.

"One big problem is that staff might not have properly collected samples for nasopharyngeal tests," Yuen said. "In the mainland a swab is inserted far into the nasal cavity. It's quite uncomfortable. But in Hong Kong the swab is not inserted far enough. Some people said they felt nothing during swab sampling, but some were inserted far enough that the people being sampled teared up.

"Whether the sampling was up to standard could be evaluated by a simple means - to test the amount of cells present in the specimens."

Yuen said the Centre for Health Protection should check all test contractors' work processes. And he suggested public laboratories should check randomly samples that tested negative by private labs to look for false negative ones.

Another government adviser, David Hui Shu-cheong of Chinese University, said 75 percent of imported cases with the mutant variant were asymptomatic.

"If there weren't mandatory tests we would never know about these cases," he said. "They would induce hidden transmission chains in the community, where asymptomatic carriers would not come forward for tests. It's very hard to trace."

He added: "Luckily, we have not seen large-scale outbreaks in the community."

Hong Kong yesterday recorded two imported cases - from Indonesia and Russia. It was the third consecutive day without new local infections.

The tally was 11,787, including 210 deaths.

jane.cheung@singtaonewscorp.com



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