Hong Kong yesterday saw a third local case of the fast-spreading Covid-19 Omicron variant with unknown source involving a 20-year-old part-time saleswoman at the SOGO department store in Causeway Bay.
The woman, who has not been vaccinated, tested preliminary positive yesterday.
She last went to work on December 28.
She lives at Aegean Coast block 8 in So Kwun Wat, Tuen Mun, and usually works and stays at a pharmacy operated by her family at H.A.N.D.S mall in Tuen Mun.
The SAR has recorded 270 confirmed Omicron cases so far, including three local cases with unknown sources, and 35 imported cases. The rest are traceable cases.
Chuang Shuk-kwan, the head of the communicable disease branch of the Centre for Health Protection, said the saleswoman tested negative on January 1 after a Covid patient visited the SOGO mall.
However, she tested positive in a required second test on January 8.
Chuang said health authorities are investigating whether the woman contracted the virus at SOGO.
"It doesn't seem like there is an outbreak at the SOGO mall and we will verify her working records at the mall," Chuang said.
She also revealed the woman went to the Tai Po Mega Mall on January 2 and dined in Sushiro restaurant between 5.30pm and 6.30pm that day.
Chuang also said a 43-year-old woman who attended liaison official Witman Hung Wai-man's birthday party tested preliminary positive yesterday.
Another preliminary positive case is an 88-year-old woman living in Ming Wah Dai Ha, Shau Kei Wan, whose masseuse family member had provided foot massage for a confirmed case. But the has masseuse tested negative so far.
The homes of all cases were locked down for compulsory tests last night.
Chuang said a 66-year-old woman living at Mei Sun Building in Tai Po also tested preliminarily positive for the virus after an Indonesian helper, her employer and the employer's teenage daughter living in the same unit a few floors below were infected.
Government advisor Yuen Kwok-yung inspected the building yesterday and said the 66-year-old living in unit 10D was likely to have contracted the virus from the trio living in unit 5D.
"The most possible reason for the infection is what we call the chimney effect, meaning warm air rises in the pipe, and in this case, in the wastewater pipe," Yuen said.
"The air reached unit 10D, where the washroom had been altered and the shower had not been used so the U-shaped trap in the drainage pipe was probably dry. So the air from floors below entered the unit and infected this lady," he said.
Centre controller Edwin Tsui Lok-kin said all households living in units 6D to 24D had to move to Penny's Bay quarantine center.
The building would be locked down again for compulsory testing. The rest of the residents have to obtain negative test results before being allowed to leave.
Meanwhile, Hong Kong recorded 33 new confirmed cases yesterday, including one of unknown source, five related to previous imported cases and 27 imported cases.
The untraceable case involved a 39-year-old cabin cleaner. She cleaned the plane of Cathay Pacific flight CX845 from New York last Tuesday, in which 11 passengers were subsequently diagnosed with the infection.
Government pandemic adviser Gabriel Leung Cheuk-wai said in a TV program yesterday that the government should further tighten social distancing measures if more cases with unknown sources are detected.
Leung, the outgoing dean of the HKU faculty of medicine, said Hong Kong is still in a critical period of the fresh wave of infections.
"If the SAR detects more cases with unknown sources, the government should consider imposing more social distancing measures including starting the Lunar New Year holiday earlier for schools and introducing extensive work-from-home arrangements."
Research by Chinese University and City University has estimated that the fifth wave triggered by the Omicron variant would lead to more than three million infections and more than 170,000 severe cases in Hong Kong if the government did not tighten the social distancing measures.
The universities found the social mobility level of Hongkongers between December 23 and January 5 - before the government's social distancing measures came into effect - has returned to the pre-pandemic level, meaning each citizen will contact 34 people per day.
"If the social contact level remained at the same level as during the Christmas and New Year holidays in the past two weeks, the fifth epidemic wave triggered by Omicron would lead to more than three million infections and more than 170,000 severe cases," the universities said.
If the social contact level can be reduced to the lowest level, the fifth wave can only cause 1,100 infections with 50 severe cases.
wallis.wang@singtaonewscorp.com
