People on the mainland are worried about spreading Covid-19 to aged relatives as they planned returns to their hometowns for holidays that the World Health Organization warns could inflame an outbreak.

The Lunar New Year holiday, which officially starts from January 21, comes after the mainland dropped its system of mass Covid lockdowns and testing.

The WHO on Wednesday said it will be challenging to manage the virus over a holiday period considered the world's largest annual migration of people.

Other warnings from top mainland health experts for people to avoid aged relatives during the holidays shot to the most-read item on the Twitter-like Weibo platform on Thursday.

"This is a very pertinent suggestion, return to the hometown...or put the health of the elderly first," wrote one user. Another user said they dare not visit their grandmother and would leave gifts for her on the doorstep.

"This is almost the New Year and I'm afraid that she will be lonely," the user wrote.

More than two billion passengers are expected to take trips over the broader Lunar New Year period, which started on January 7 and runs for 40 days, the country's transport ministry has said. That is double last year's trips and 70 percent of those seen in 2019 before the pandemic emerged in the central Chinese city of Wuhan.

But outbound travel is not expected to pick up dramatically for the period. After three years of isolation from the outside world, mainland authorities on Sunday dropped quarantine mandates for inbound visitors in a move expected to eventually also stimulate outbound travel.

However, concerns about the mainland’s outbreak have prompted more than a dozen countries to demand negative Covid test results from people arriving from China. Among them, South Korea and Japan have also limited flights and require tests on arrival, with passengers showing up as positive being sent to quarantine.

Beijing has in turn stopped issuing short-term visas and suspended transit visa exemptions for South Korean and Japanese nationals.

Despite Beijing's lifting of travel curbs, outbound flight bookings from China were at only 15 percent of pre-pandemic levels in the week after the country announced it would reopen its borders, travel data firm ForwardKeys said on Thursday.

Low airline capacity, high airfares, new pre-flight Covid-19 testing requirements by many countries and a backlog of passport and visa applications pose challenges as the industry looks to recovery, ForwardKeys Vice President Insights Olivier Ponti said in a statement.

Hong Kong Airlines, meanwhile, on Thursday said it does not expect to return to capacity until mid-2024. (Reuters)