Chinese officials warn deadly virus can be spread before people show any sign of infection

At home, by Sunday evening some 52 people across Scotland, England, Wales, and Northern Ireland had been tested for the virus but all were negative. Another person in Scotland, the sixth, was checked and given the all-clear.

Health Protection Scotland has urged travellers returning from Wuhan, the epicentre of the outbreak, who become unwell within a fortnight from a sore throat, cough or breathing difficulties to call their GP or NHS 24.

Officials in China announced an immediate ban on the sale of all wildlife. The virus is thought to have originated in animals although no cause has been officially identified.

In humans, the incubation period, during which a person has the disease but shows no symptoms, ranges from between one and 14 days. Without symptoms, a person might not be aware they are infected and yet still be able to spread it.

On Sunday, UK ministers suggested the Government was keeping open the option of airlifting back to Britain up to 200 Britons trapped in Wuhan city.

Stephen Barclay, the Brexit Secretary, said the Government was “closely monitoring the situation”.

He was asked how UK citizens could get out of Wuhan in Hubei province, as urged to do so by the Foreign and Commonwealth Office[FCO], when all the airports there were closed and the city was in lock-down.

Mr Barclay said: “It’s a fast-moving situation and one that we are monitoring. The FCO is working with the Chinese authorities in that regard.”

While some 2,000 people had come into Heathrow Airport from Wuhan, the Secretary of State confirmed only 31 people had been tested for the virus; all had proved negative for it. He said the authorities had been “reaching out” to people and that was ongoing.

“We are unfortunate in that we have many of the world experts in this field here in the UK and are obviously informing our approach. Work is going on on that and if people have the symptoms, they should report it. But all the tests so far have proved negative,” he told the BBC’s Andrew Marr Show.

Pressed if an airlift was being considered, the Secretary of State replied: “We continue to monitor it…We keep it under review.”

A Commons update to MPs is expected on Monday and another meeting of Whitehall’s emergency Cobra committee could also meet again in the next 48 hours.

There are also no confirmed diagnoses in UK citizens abroad. The risk to the public in Britain is still classed as “low”.

Priti Patel, also asked about a possible airlift, said the Government was “looking at all options”.

"Right now, in terms of the urgency of the situation, and rightly so, we are working with the Chinese authorities, the World Health Organisation and Public Health England to look at what is going on and to ensure we are doing our utmost to stop the virus coming to the United Kingdom and obviously becoming a widespread problem,” added the Home Secretary.

The FCO has updated its guidance to "advise against all travel to Hubei province", which has been on lockdown for several days as China seeks to contain the illness.

But the guidance also adds: "If you are in this area and able to leave, you should do so. This is due to the ongoing novel coronavirus outbreak."

Earlier, Shinzo Abe, Japan’s Prime Minister, said his country would evacuate any of its citizens in Wuhan who wished to return to Japan.

His comment came as Japan reported its fourth case of the fatal virus. France also pointed to the possibility of arranging emergency flights out of Wuhan.

America reported its third case of the virus. A person from Wuhan tested positive in California. The patient is now in isolation at a local hospital and said to be in a good condition.

Other countries with confirmed cases include France, Canada, Australia, Vietnam, Thailand and South Korea.