People wearing masks cross the road in the Central area of Hong Kong, July 27, 2020. (WANG SHEN/XINHUA)

HONG KONG – Hong Kong health authorities are investigating a preliminary positive local COVID-19 infection involving the L452R mutant strain.

The source of origin of the case that involved a 27-year-old man who lives in Tai Po remained unknown, according to a spokesman for the Department of Health’s Centre for Health Protection.

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In a statement issued Wednesday evening, the spokesman said the patient lives at Wan Hang House in Wan Tau Tong Estate and developed symptoms including fever on Monday.

The man, who is an airline ground crew staff member and has come into contact with cargo flight crews at Hong Kong International Airport, has no recent travel history

He sought medical help on Tuesday and tested preliminarily positive with the L452R mutant strain.

The man, who is an airline ground crew staff member and has come into contact with cargo flight crews at Hong Kong International Airport, has no recent travel history.

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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 went to work on June 22, the spokesman said.

The patient has not received COVID-19 vaccination.

The government has issued a compulsory testing order for the building where he lives. Residents of Wan Hang House are required to stay in their flats and undergo compulsory testing. The government said it aimed to finish the exercise at about 7:30 am Thursday.

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Earlier on Wednesday, a number of housing estates in Tai Po were also put under a compulsory testing order as “a very high viral load” has been detected in the sewage samples collected in the area, indicating that the virus may have been transmitting in the neighborhood.