Hong Kong confirmed the first Omicron case which has entered the community on Saturday -- a 36-year-old male Cathay Pacific crew member who operated cargo flight CX2071 from Anchorage in the United States, which arrived in Hong Kong on December 13.

He tested negative at the Hong Kong International Airport and stayed home during a three-day enhanced medical surveillance period. He headed out last Wednesday to buy food and to undergo a Covid-19 test at a mobile testing station in his neighborhood.

He tested positive on Wednesday and developed symptoms on the same day, triggering a lockdown of his residence at Cheung Hing Building on Pitt Street in Yau Ma Tei on Thursday night.

Cathay Pacific said the aircrew member had not left his home except for one outing where he took the mandatory Covid-19 test and made food purchases during the 3-day enhanced medical surveillance period since his arrival.

Six places he visited in Yau Ma Tei, Tsim Sha Tsui and Mong Kok have been slapped with mandatory testing notices.

"The authorities have taken various measures to detect and prevent community cases," Chan said. "Once relevant cases are found, the area will be locked down for testing."

She stressed that current research showed that Omicron may escape immunity from past infections or vaccination, urging the elderly and high-risk groups to receive booster jabs as soon as possible.

Respiratory disease expert David Hui Shu-cheong said in a television program that there were hidden concerns about home quarantine for flight crew, and that they may spread the coronavirus every time they leave home for Covid tests.

He suggested the authorities consider sending staff to collect samples for the crewmen, so that they do not need to head out for tests.