The Centre for Health Protection today said it is investigating four additional imported COVID-19 cases involving patients who arrived from the UK, Russia and Indonesia.

Three cases involved mutant strains while the mutation test result of the remaining case is pending.

The patients, two men and two women aged 32 to 58, arrived in Hong Kong from Group A specified, or high-risk, places. Three of them tested positive during the test-and-hold arrangement upon arrival at Hong Kong International Airport while the remaining patient tested positive on the ninth day of quarantine.

Meanwhile, the centre is investigating an overseas COVID-19 case involving an 18-year-old man who lives at Block 7, King's Park Villa in Ho Man Tin.

He tested negative in Hong Kong on September 29 and travelled to the UK on October 1 on British Airways flight BA032. His specimen collected in the UK on October 3 tested positive and he developed symptoms on October 11.

The man had received two doses of the BioNTech vaccine on March 20 and April 10 in Hong Kong. He works at 31/F, Two Pacific Place, 88 Queensway in Admiralty, and last went to work on September 24.

The centre is following up on the case with the UK health authorities, while epidemiological investigations and contact tracing are ongoing.

As a prudent measure, the places where the patient stayed and worked in Hong Kong during the incubation period will be included in a compulsory testing notice.

Specified people who were present at the relevant venues during specified periods must undergo compulsory testing.

Two schools or their specified levels are also covered in the compulsory testing notice due to an outbreak of upper respiratory tract infection or influenza-like illness.

The Food & Health Bureau added that the testing deadline for the above compulsory testing notice will be extended by one day to October 15, in view of the anticipated inclement weather in the next few days.

The testing period will be further extended for one day if Tropical Cyclone Warning Signal No. 3 or above, or the Red or Black Rainstorm Warning Signal or the post-super typhoon extreme conditions announcement by the Government is in force at any time during the period for undergoing compulsory testing.

Members of the public are advised to check the opening arrangements of community testing centres and mobile specimen collection stations.

A total of 72 cases were reported in Hong Kong in the past 14 days, one of which is a local case with an unknown infection source and the rest are imported.

For information and health advice on COVID-19, visit the Government’s dedicated webpage.