The patients, aged between 32 and 58, flew in from Indonesia, Russia and the United Kingdom. Two of them are cabin crew members, and all of them were fully vaccinated and asymptomatic.
Three of the patients were found to be carrying a mutated virus strain.
Separately, the Centre for Health Protection said a man had tested positive for the coronavirus in the UK, two days after he left Hong Kong.
The 18-year-old, who was on flight BA032, was fully vaccinated and tested negative for the virus two days before his departure.
The patient lived in Block 7 of King’s Park Villa in Ho Man Tin, and the CHP has ordered anyone who had stayed there to get tested.
People at the man’s workplace, the 31st floor of Two Pacific Place in Admiralty, have also been ordered to get tested. He last went to work there on September 24.