An expected influx of returnees from overseas might bring new variants of the novel coronavirus into Hong Kong, which is battling its worst COVID-19 outbreak, an expert warned ahead of the lifting of a ban on flights from nine countries.

Respiratory disease expert Leung Chi-chiu warned of a possible influx of new variants when the city resumes inbound flights from nine main source countries, including the United States, the United Kingdom, Canada and the Philippines, from April 1.

To identify possible new variants without delay, COVID-19 tests at the airport and genomic sequencing of the novel coronavirus of the samples collected need to be performed stringently, he said.

Leung suggested the government control the number of inbound travelers by managing the supply of rooms at the designated hotels where arrivals will be quarantined, saying that would prevent too much pressure being put on the city's genomic sequencing work.

Travelers arriving at the same time should be grouped for quarantine to avoid being infected by latecomers, he said.

On Monday, the government announced the lifting of the flight bans from the start of next month and said arrivals could be discharged from designated quarantine hotels if they test negative on the fifth, sixth and the seventh day after arriving. They would then undergo seven days of home observation.

There are 44 designated quarantine hotels in the city. There are no vacancies for most of the 25 available next month, and some in Kowloon are booked out through to July. Some hotels will not accept bookings until May.

Timothy Chui Ting-pong, executive director of the Hong Kong Tourism Association, told a radio program that over 10,000 people are expected to return to the city from overseas in May for the summer break. To cope with the expected surge in demand, he suggested the government include more hotels in the quarantine scheme.

Hong Kong Chief Executive Carrie Lam Cheng Yuet-ngor told a daily COVID-19 briefing on Wednesday that the lifting of the flight bans is not a relaxation as only Hong Kong residents are allowed to return and they will be subjected to stringent quarantine measures.

Lam said that before boarding their flights, returning residents need to be vaccinated, have tested negative for COVID-19 in the previous 48 hours and have a reservation at a designated quarantine hotel.

She also said that a flight circuit breaker mechanism for the nine countries is necessary to encourage airlines to follow Hong Kong's pandemic rules.

Lam stressed that Hong Kong's goal in its battle against the pandemic is to protect the lives of residents－a priority in line with that of the nation.

"We will not 'lie flat' or take any chances," she said.