The Centre for Health Protection today said it is following up on two confirmed COVID-19 cases with test results involving the N501Y mutant strain.

The cases involve two female domestic helpers aged 46 and 38. They live in their employers' residences at Block N2 of Kornhill in Quarry Bay and Royalton in Pok Fu Lam.

The 46 year-old patient has been classified as a local case, while another patient is epidemiologically linked with the former case.

As the N501Y mutant strain is with higher transmissibility, the centre decided to carry out prudent measures on infection control and prevention to stop the potential risk of spreading the mutant strain.

It will send asymptomatic residents of all units in the two buildings to quarantine centres for 21 days of compulsory quarantine.

Symptomatic residents will be sent to the hospital for treatment.

Block N2 of Kornhill involves around 230 units, while Royalton has about 30 units, the centre explained.

Earlier at midnight, the Government made restriction-testing declarations to require people in Block N2 of Kornhill and Royalton to stay in their premises and undergo compulsory testing for COVID-19.

According to the compulsory testing notice, any individual who had been at the buildings for more than two hours from April 21 to May 4, even if they were not present in the restricted areas at the time when the declarations took effect, must undergo compulsory testing by May 6.