Britain’s embassy in Beijing has said it is “working to make available an option” for British nationals to leave the Chinese province at the centre of the coronavirus as the UK’s response was contrasted with that of other countries with active evacuation plans.

The announcement on Monday came as the former foreign secretary, Jeremy Hunt, backed the idea of airlifts for British citizens in China and Public Health England said the first case of the virus was likely to come from somebody already in the UK.

“Our view is that, although airports are important, the most likely place that we might find a case is somebody in the country already, and it’s absolutely critical that the public health service and the NHS are ready to diagnose that and are able to designate the person to the right facilities,” said Prof Yvonne Doyle, the medical director and director of health protection for PHE.

The head of the World Health Organisation will hold a special meeting with officials in Beijing on Monday to discuss how to contain the coronavirus that has killed 80 people and left more than 400 in a critical condition.

In an effort to reduce chances of infection during what is China’s busiest travel season, officials announced the end of this week’s lunar new year holiday would be postponed until at least 2 February. Authorities have also widened sweeping restrictions on travel across the country.

On Monday, Chongqing municipality, which has a population of 30 million, said it had banned long-distance bus services. The municipality borders Hubei province, where the vast majority of deaths have been recorded. It follows similar announcements over the weekend by Beijing, Shanghai and the eastern province of Shandong.

The suspension of long-distance bus services, the cheapest way to travel, is likely to slow down the return of millions of migrant workers who have visited their families over the lunar new year.

By postponing the end of the holiday to Sunday from Friday, officials hoped to “effectively reduce mass gatherings” and “block the spread of the epidemic,” a cabinet statement said.

Many of China’s big retail chains have also said they will temporarily close their stores, while some online businesses and banks have advised employees returning from Hubei province to work from home.

The Australian government does not know how many of its citizens are caught in the vast quarantine lock-down imposed across China, as it and governments around the world scramble to try to evacuate their nationals.

But it appears increasingly unlikely foreign countries will be allowed to simply extricate their citizens in the face of militarily enforced lockdowns. Indonesia has said it “seems to be impossible”, while Australia has said it “needs to abide by the travel restrictions … placed there for precisely the purpose of containing the coronavirus”.

A hotline for family members of Australian citizens has received 385 calls, but the foreign minister, Marise Payne, has said it was “unwise to speculate” on how many citizens this represented or how quickly they could be brought out.