A 63-year-old man residing at block 5, Lei Muk Shue Estate in East Tsuen Wan was identified as Hong Kong's No 1,052 patient after his 66-year-old wife and five-year-old granddaughter tested positive the previous day. Photo: Google Maps

Thousands of people in Tsuen Wan in the New Territories were asked by the Centre for Health Protection to submit saliva samples for Covid-19 testing after three residents were infected by the virus.

On Thursday, a 63-year-old man was identified as Hong Kong’s No 1,052 patient after his 66-year-old wife and five-year-old granddaughter tested positive the previous day. All three cases have been categorized as local infections, according to the Centre for Health Protection.

The newly identified patient, who resides with his wife in block 5, Lei Muk Shue Estate in East Tsuen Wan, was asymptomatic and had no recent travel history, said Chuang Shuk-kwan, head of the communicable disease branch of the Centre for Health Protection. He was working in his small watch repair shop on the ground floor of Cheuk Ming Mansion, where his son lives.

Chuang said the possibility that the man was infected earlier than his wife and granddaughter could not be ruled out.

The Centre for Health Protection was trying to identify and contact the man’s customers but he did not keep records. It has so far delivered 47 bottles in Cheuk Ming Mansion and 18 bottles in Yeung Uk Road Market for people to send in their deep-throat saliva samples for voluntary tests. It also planned to deliver thousands of bottles to the residents of 850 units in Lei Muk Shue Estate on Thursday.

Secretary for Food and Health Sophia Chan Siu-chee said the new local infections could be caused by asymptomatic virus carriers. Chan said the scale of virus testing in the community needed to be expanded.

Unless more clusters are identified across Hong Kong, there is no immediate need to reintroduce a series of social distancing measures that were withdrawn last week, said Siddharth Sridhar, an assistant professor of microbiology at the University of Hong Kong.

The public should not panic about the new cases but should remain vigilant, said Sridhar.

“The difficulty with this new virus is that it’s highly infectious,” said David Hui Shu-cheong, chairman, Department of Medicine and Therapeutics, Faculty of Medicine, Chinese University of Hong Kong. Residents who return from overseas may still carry the virus after the 14-day home quarantine period and spread the virus in the community, he said.

“We will have sporadic cases occasionally, as long as the sporadic cases are not leading to major community transmission, then we can still continue the usual activities,” Hui said.

It may be unrealistic to achieve a target of 28 consecutive days of no local transmissions in order to fully relax social distancing measures, Leung Chi-chiu, the chairman of the Medical Association’s advisory committee on communicable diseases, said in a radio program on Thursday.

It might be impossible to stop the spread of Covid-19 completely because so many people enter Hong Kong every day, Leung said.

He said the reappearance of new local infections showed that the home-quarantine measure for incoming travellers has been insufficient. He said if the measure cannot completely stop virus transmissions, there is still a risk of a community outbreak in Hong Kong.

However, Leung said the resumption off secondary school classes on May 27 should not be affected.

Read: Local infections reappear in Hong Kong

Read: HK to relax social distancing rules from Friday