All Britons in China should leave the country if they can to minimise the risk of exposure to the coronavirus, the Foreign Office has said.
The UK says it will charter another flight on Sunday to evacuate British nationals and their families from Wuhan, where the virus originated.
Commercial flights are available from other parts of China.
Meanwhile, a Belgian woman, who was on a flight bringing UK citizens back on Sunday, tested positive for the virus.
Eleven UK citizens and family members were on the woman's flight, which carried passengers from 30 other countries to France, before the Britons flew on to RAF Brize Norton in Oxfordshire.
Of these, 10 continued to Arrowe Park Hospital on the Wirral for a 14-day period of isolation, while Anthony May-Smith was taken to hospital in Oxford to be tested for potential coronavirus.
At least 427 people have died after contracting the virus and there have been more than 20,000 confirmed cases, most of them in China.
There are an estimated 30,000 UK nationals in China, ministers have said.
The Foreign Office earlier said it continued to work to evacuate Britons from Hubei province where the outbreak began.
Foreign Secretary Dominic Raab said: "We now advise British nationals in China to leave the country if they can, to minimise their risk of exposure to the virus.
"Where there are still British nationals in Hubei province who wish to be evacuated, we will continue to work around the clock to facilitate this."
The latest Foreign Office advice added that the elderly and those with pre-existing medical conditions may be at heightened risk.
The virus has now spread to more than two dozen nations, including two cases in the UK.
However, the World Health Organization (WHO) said it does not yet qualify as a "pandemic". This is declared only when there are sustained outbreaks within communities in multiple parts of the world, according to the WHO.
Previously the Foreign Office had advised against all but essential travel to China, while warning against any travel to Hubei province, including the city of Wuhan.
BBC China correspondent Robin Brant said the new advice was "not because we've seen a sudden increase in the severity of the outbreak of the virus".
Instead, he said it appeared to be prompted by the Foreign Office organising what it was calling "the last flight" to evacuate Wuhan.
The UK was also moving non-essential staff out from its embassy and consulates in China, so "there are fewer people who can help any Britons in distress", he said.
One British man in China who fears he contracted the new coronavirus in November said he had been given no indication of when he will be able to leave Wuhan.
Jamie Morris, 23, from Tredegar in South Wales, said he had not been able to return on recent flights because he had given his passport to Chinese authorities to extend his residency permit.
"I am currently on my own in my apartment, isolated from the outside world," he said.
'I feel like I want to stay'
Some Britons in China told the BBC that they intend to stay despite the Foreign Office advice - while others questioned whether it was possible to leave.
Music teacher Sam Mulliner and his wife, Rebekah, work at an international school in Shanghai and say it is not easy to "just get up and leave".
"I feel like I want to stay here and support my Chinese colleagues," he said, adding that there may be more risk of infection on a plane.
John Hall said he wants to return to the UK with his Chinese wife and his three-month-old daughter from his home in Zhanjiang.
But he said he cannot travel the six hours to the nearest embassy to get the paperwork and feared his daughter is "much too young" to fight the virus if she should contract it.
"We don't want to be split up," he said.
"I would be devastated."
On Friday, 83 UK citizens were repatriated on a flight out of Wuhan arranged by the UK government. Another 11 Britons joined them on Sunday on a French flight.
They are now in quarantine at Arrowe Park Hospital in Wirral for 14 days - the incubation period of the virus - to ensure that they are not infected.
A further eight UK nationals and six of their family members left China on a flight to New Zealand on Tuesday, the Foreign Office has said.
But shadow foreign minister Afzal Khan said the evacuation of Wuhan had been a "shambles", citing delays, lack of information and "the terrible cases of family separation that have occurred".
The only two UK airlines serving China - British Airways and Virgin Atlantic - have suspended their flights between the UK and China due to fears about the spread of the virus.
All flights with Chinese Airline Hainan between Manchester and Beijing will also be suspended from Thursday to 28 March, Manchester Airport said. UK passengers have been advised to contact the airline on 0161 236 6184.
Two people, a student at the University of York and one of their relatives, are being treated for coronavirus at the specialist infectious diseases unit at Newcastle Royal Victoria Infirmary.
They are the UK's only two confirmed cases, with 414 people having tested negative for the virus, according to the Department of Health.
Meanwhile, the World Health Organization (WHO) said on Tuesday that there is a "window of opportunity" to stop the deadly new coronavirus becoming a broader global crisis.
It said that the steps China took to fight the virus at its epicentre were a good way of stopping its spread.
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