The number of people killed in China by the new coronavirus has risen to 82, including the first reported death in the capital, Beijing - a city of over 20 million.
The prime minister Boris Johnson said the government was doing "everything we can" to help Britons in coronavirus-hit Hubei province while those returning from Wuhan were told to "self-isolate" even if they have no symptoms.
While plans were underway to get British nationals out of the region, Public Health England acknowledged that the first UK case is likely to come from somebody already in the country.
After earlier refusing to commit to getting Britons out of Hubei province, the capital of which is Wuhan, the Foreign Office said on Monday they were making evacuation plans and said anyone in the province who needs assistance can call a 24-hour helpline.
A Foreign Office spokesman said: "We are working to make an option available for British nationals to leave Hubei province due to the heavy travel restrictions and increased difficulty of accessing consular or medical assistance."
It added: “We are working to make available an option for British nationals to leave Hubei province.
“We continue to monitor developments closely and are in close touch with the Chinese authorities."
“Please continue to check our travel advice on gov.uk for updates."
In a significant ramping up of the precautions in the UK around the virus, health secretary Matt Hancock said officials could not be 100% certain that the virus is not spread by people who are not displaying symptoms.
The move means around 1,500 people who have returned from Wuhan since January 10 should isolate themselves for 14 days from the date of leaving China for the UK.
The number of people now tested for coronavirus in the UK stood at 73 on Monday afternoon. All tests have come back negative, the Department of Health and Social Care said in a statement.
Mr Johnson told reporters on Monday: "We are looking at everything we can to give reassurance to those people in Wuhan and you will be hearing a bit more in due course but I don't want to pre-empt the decisions we are going to make."
He said travellers arriving in the UK would be "properly screened and checked if they have come from an area that is known to have the infection".
"So far there is still no case of somebody with coronavirus here in the UK but clearly there are a lot of cases in China and it is spreading."
Earlier, Professor Yvonne Doyle, medical director and director of health protection for PHE, warned the first UK case is likely to come from somebody already in the country.
In an interview with Sky News, she said: “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.
“That’s the most likely scenario we are dealing with.”
Professor Peter Openshaw from Imperial College told ITV News that there was "bound" to be cases in the UK.
"It won't be a surprise when we start to see cases. the question is going to be how much onward transmission there's going to be in other cities," he said.
The number of those infected by the illness in China has climbed to 2,744, including cases five cases in Hong Kong and two in Macau.
The Chinese government has extended the Lunar New Year holiday until Sunday in a bid to keep people at home and stop the virus from spreading.
Hong Kong has said it will bar entry to visitors from the mainland following a warning from China's health minister the virus’s ability to spread was increasing and that the disease is infectious before symptoms start to show.
Other cases have also been found in Thailand, Taiwan, Japan, South Korea, the US, Vietnam, Singapore, Malaysia, Nepal, France, Canada and Australia.
Prof Doyle said efforts were continuing to trace the 2,000 people who have entered the UK from China on international flights.
Chinese President Xi Jinping has and said the government was stepping up efforts to restrict travel and public gatherings while rushing medical staff and supplies to the city at the centre of the crisis, Wuhan, which remains on lockdown.
State media reported that the president had visited the virus-hit region over the weekend to meet with officials - a sign as to how serious the Chinese are taking this.
The new virus comes from a large family of what are known as coronaviruses, some causing nothing worse than a cold.
It causes cold-and flu-like symptoms, including cough and fever, and in more severe cases, shortness of breath.
It can worsen to pneumonia, which can be fatal.
The majority of those who have so far died have been elderly or had pre-existing medical conditions.
The epidemic has revived memories of the SARS outbreak that originated in China and killed nearly 800 as it spread around the world in 2002 and 2003.
The coronavirus's spread has come amid China’s busiest travel period of the year, when millions crisscross the country or head abroad for the Lunar New Year holiday.
In a bid to block the spread of the epidemic, the government pushed back the end of the holiday to Sunday from Thursday and schools will remain closed until further notice, the Cabinet said.
Tens of millions of people were due to crowd into planes, trains and buses to return to work after visiting their hometowns or tourist sites for the holiday.
Chinese travel agencies have also been told to halt all group tours and attractions such as both Disney parks in Shanghai and Hong Kong have closed.
China's health commission said anyone travelling from Wuhan is now required to register with community health stations and quarantine themselves at home for 14 days — the virus’ maximum incubation period.
In the heart of the outbreak – where 11 million residents are already on lockdown – Wuhan has banned most vehicle use, including private cars, in inner city areas.
China cut off trains, planes and other links to the city on January 22 and has steadily expanded the lockdown to 16 surrounding cities with a combined population of more than 50 million.
Video footage captured in Wuhan by resident Lin Wenhua shows a city shut off from the outside world, as he travels through empty streets of the city.
Mr Lin said people in the city at the centre of the outbreak are "fearful and anxious" but people "are facing the situation in a positive way".
Wuhan is building two makeshift hospitals with about 1,000 beds each to handle patients.
The city has said the first is expected to be completed on February 3.
Medical workers in Wuhan have been among those infected and local media reported a doctor died on Saturday morning.
The 62-year-old physician was hospitalised on January 18 and died a week later.
Xinhua said medical supplies are being rushed to the city, including 14,000 protective suits, 110,000 pairs of gloves and masks and goggles.
The commission said it is bringing in medical teams to help handle the outbreak and the Chinese military dispatched 450 medical staff, some with experience in past outbreaks, including SARS and Ebola, Xinhua reported.