Hong Kong announced a two-week ban on incoming flights from eight countries, including Pakistan and India, and tightened restrictions on Wednesday as authorities feared a fifth wave of Covid-19 infections.

The restrictions were announced as health authorities scoured the city for the contacts of a Covid-19 patient, some of whom had been aboard a Royal Caribbean ship that was ordered to cut short its “cruise to nowhere” and return to port.

Incoming flights from Australia, Canada, France, India, Pakistan, the Philippines, Britain and the United States, including interchanges, would be banned from Jan 8 to Jan 21, Hong Kong leader Carrie Lam told reporters.

Lam said the government would ban indoor dining after 6:00pm from Friday, and close swimming pools, sports centres, bars and clubs, museums, and other venues for at least two weeks. Future cruise journeys would be cancelled.

“We're yet to see a fifth wave yet, but we're on the verge,” Lam said.

Hong Kong recorded 38 new coronavirus cases on Wednesday, but only one was a local community transmission, while the rest were people who had returned to the city and tested positive during quarantine.

The global finance hub has stuck to a zero-tolerance strategy by largely isolating itself from the world and enforcing a draconian and costly quarantine regime.

On Dec 31, a streak of three months without community cases ended with the first local transmission of the Omicron variant.

Since then, authorities have scrambled to track down and test hundreds of people who had been in contact with a handful of Omicron patients.

One patient, however, had no known links, raising fears of a large outbreak.

“We are worried there may be silent transmission chains in the community,” Lam said.

Lam said the government would not suspend classes for the time being “for the benefit of children”.

In response to the outbreak fears, Standard Chartered Plc has started operating in split teams in Hong Kong, a bank spokesperson said.

Dancing cluster The latest contact tracing campaign was sparked by a patient who danced with some 20 friends in a central park on New Year's Eve. Two of the fellow dancers, one of whom was a domestic helper, came up positive in preliminary tests.

The helper's employer and eight other of her close contacts then went on a cruise on Jan 2.

As part of its coronavirus restrictions, Hong Kong has restricted cruises to short trips in nearby waters, with ships asked to operate at reduced capacity and to only allow vaccinated passengers who test negative for the virus.

The “Spectrum of the Seas” ship, which returned a day early, had about 2,500 passengers and 1,200 staff on board.

The nine close contact passengers tested negative for the virus so far, authorities said.

“Spectrum of the Seas is taking appropriate measures under guidelines by the Department of Health,” Royal Caribbean told Reuters in a statement.

The nine close contacts were sent to a quarantine centre, while the rest of the passengers and staff will have to undergo several tests, the government said.

Additionally, people who have been to dozens of places across Hong Kong around the same time as the close contacts of recent patients have been issued compulsory testing notices, the government said in a separate statement.

Victoria Park, in downtown Hong Kong, the newly opened M+ modern art museum, ferry piers, restaurants, stores, clinics were among the places listed.

Gabriel Leung, University of Hong Kong dean of medicine and a government adviser, told public broadcaster RTHK there were probably “five-to-10 invisible transmission chains” in the city.

“There's no time to waste,” Leung said. “We need circuit-breaker measures.”