The Centre for Health Protection today said that it is investigating a preliminary positive imported-related COVID-19 case involving mutant strains.

As such, the Government made a restriction-testing declaration effective from 7.30 this evening at On Hei House (Block A), Siu Hei Court in Tuen Mun, under which people within this specified restricted area are required to undergo compulsory testing.

The 64-year-old male patient is a toilet cleaner at Hong Kong International Airport. He finished his COVID-19 vaccination course in August and tested negative in 10 tests during December 2 to 20.

Yesterday, his specimen tested preliminary positive with a cycle threshold (Ct) value of about 27 to 32. He developed symptoms the same day. The spike protein gene of his sample involves the N501Y and T478K mutant strains.

The centre suspects that the patient carries the Omicron variant, but a whole genome sequencing needs to be conducted to confirm the result.

Without a recent travel history, the patient last went to work yesterday. He mainly performs cleaning and disinfection work at a toilet solely used by preliminary positive imported cases waiting for transfer to hospital. This toilet is confined to a designated area at the airport's Midfield Concourse.

He had stayed in the storeroom inside the toilet during work and had been in that toilet with preliminary positive cases at the same time. An initial investigation showed that he had likely acquired the infection while working at the toilet.

The centre conducted a site visit there today and collected 26 environmental samples at the storeroom, changing room and restroom used by the patient. Test results are pending.

Furthermore, the centre advised the Airport Authority and the contractor concerned that the cleaners should only carry out cleaning and disinfection work after the preliminary positive cases have left the toilet, and that cleaners should not stay inside the toilet storeroom when they are not performing work.

Since the patient carries a mutant strain, the Government made a restriction-testing declaration this evening for On Hei House in Tuen Mun where the patient lives. At the same time, people who live or work in On Hei House will be subject to increased compulsory testing frequency. The places where the patient had visited in Hong Kong during the incubation period will also be included in a compulsory testing notice which requires specified people to get tested.

Citizens in the restricted area have to get tested before 1.30am on December 24. The Government aims to finish the exercise at around 7am tomorrow.

Those in the restricted area who have undergone virus testing from December 21 to 23 and are able to provide a proof are not required to take the test again.

However, people who had been in On Hei House for more than two hours from December 1 to 23, even if they were not present in the restricted area at the time when the declaration took effect, must undergo compulsory testing on or before December 25. Vaccinated people will not be exempted.

Separately, the Hospital Authority said in a press release that around 100 staff had to undergo virus testing, as the 64-year-old patient had attended a consultation session at Tuen Mun Wu Hong Clinic on December 13, and had accompanied another person to the specialist outpatient clinic of Tuen Mun Hospital’s Department of Oncology on December 17 and 20.

All staff wear masks during work and none of them have been identified as a close contact, the authority noted, adding that thorough cleansing and disinfection will be carried out at areas visited by the patient.