The Centre for Health Protection said today it is investigating four preliminary positive imported COVID-19 cases, adding that one of the patients has a high viral load.

The first two cases involve two men, aged 29 and 57, who live in Harbour Pinnacle in Tsim Sha Tsui and a house in Headland Village in Discovery Bay. They work for the same airline as cargo flight crew members and tested negative on October 26 and 29 respectively.

The two patients travelled to Germany on October 31 and returned to Hong Kong on November 6 by the same flight. Their specimens collected upon arrival at Hong Kong International Airport tested negative for COVID-19.

They underwent compulsory testing in accordance with relevant requirements for exempted people. Their samples collected yesterday tested preliminary positive for the virus and carried the L452R mutant strain, with Ct values of 13 to 16 and 31 to 34.

The centre noted that both patients received two doses of the BioNTech vaccine in April and May in Hong Kong. The 29-year-old man has had symptoms since November 8 while the 57-year-old patient remains asymptomatic.

Due to the presence of a mutant strain with higher transmissibility and infection risk, the Government made a restriction-testing declaration tonight for the Harbour Pinnacle in Tsim Sha Tsui where the 29-year-old patient stayed in Hong Kong.

For the house where the 57-year-old patient lived, relevant residents have been arranged to undergo quarantine.

The places where the two patients had visited in Hong Kong during the incubation period will also be included in a compulsory testing notice.

Another case involves a 30-year-old woman who is a foreign domestic helper and had received two doses of COVID-19 vaccination in the Philippines. She arrived in Hong Kong from that country on October 17.

She was tested six times during her stay at a designated quarantine facility and all the results were negative. Upon completion of the compulsory quarantine on November 7, she moved to Rosedale Hotel in Causeway Bay.

She underwent another test on November 8 and the result was positive but with a low viral load.

The remaining case involves a 15-year-old girl who arrived from Italy via Qatar on October 14. She also underwent six tests during the compulsory quarantine period and the results were all negative.

After completing the compulsory quarantine on November 4, the patient stayed at Gateway Hotel, Hong Kong in Tsim Sha Tsui. She tested positive on November 8 with a Ct value of 27 to 29.

The centre said it cannot exclude the possibilities that these two cases involving female patients are re-positive ones. It will monitor their further testing results after admission to hospital.

In view of these four cases who had stayed in Hong Kong during the incubation period, 29 specified premises are included in compulsory testing notice. People relating to these cases have to strictly follow the compulsory testing requirements.

Eight schools with outbreak of upper respiratory tract infection or influenza-like illness are also covered in the compulsory testing notice.

The Government will set up mobile specimen collection stations at Granville Road in Tsim Sha Tsui East, Hankow Road in Tsim Sha Tsui and the open area next to Discovery Bay Fire Station tomorrow to provide free testing service for those subject to compulsory testing.