The Centre for Health Protection today said it is investigating a local preliminary positive COVID-19 case from an unknown source involving the L452R mutant strain.

The Government made a restriction-testing declaration for the residential building in Tai Po where the male patient lives.

The 27-year-old man resides at Wan Hang House in Wan Tau Tong Estate. He developed symptoms including a fever, sore throat and cough on June 21 and consulted a private doctor that day.

The deep throat saliva sample submitted the following day tested preliminary positive and carried the L452R mutant strain.

The patient is an airline ground crew member at Hong Kong International Airport, where he had received cargo flight crews. He last went to work at the airport on June 16.

He also worked part-time to provide customer service at Uptown Plaza in Tai Po, where he last worked on June 22. Preliminary information revealed that he has no recent travel history.

The Government decided to make a restriction-testing declaration for Wan Hang House as the risk of infection in the relevant area may be higher.

The declaration took effect from 7pm and aims to be finished by about 7.30am tomorrow. People in the area subject to compulsory testing will need to be tested by 2am.

They will need to undergo a nucleic acid test at temporary specimen collection stations set up there, where staff will collect samples through combined nasal and throat swabs.

The Government will arrange door-to-door specimen collection for people with impaired mobility and seniors.

People in the restricted area who have undergone testing from June 21 to 23 and can provide a SMS notification through a mobile phone or related certification containing the test results are not required to take the test again.

However, they must stay in their premises until all such people identified in the area have undergone testing and the test results are mostly processed.

Meanwhile, according to the compulsory testing notice, any person who had been at that building for more than two hours from June 3 to 23, even if they were not present in the restricted area when the declaration took effect, must undergo compulsory testing by June 25.

In addition, those residing in the same building as a confirmed local case with the mutant strain are subject to compulsory testing on the third, seventh, 12th and 19th day counting from the day the case is announced.

The Home Affairs Department has set up a hotline 2835 1473 for the affected residents to make enquiries and seek assistance.

Eight places visited by the preliminary positive case and schools within the specified area in Tai Po are also covered by the compulsory testing notice.

Meanwhile, a school in Sham Shui Po where upper respiratory tract infection and influenza-like illness has occurred has also been covered by the compulsory testing notice.