There is an “increased likelihood” of cases of the new coronavirus occurring in the UK, Health Secretary Matt Hancock has said.
Globally, there are more than 500 confirmed cases of the virus, which has killed 18 people in China.
But there are no known cases in the UK, Mr Hancock said, which was “well prepared” to deal with an outbreak.
However, six people are being tested in hospitals in Scotland and Northern Ireland after showing symptoms.
All the patients had been in Wuhan – the Chinese city where the new strain of the virus, which can cause lung disease such as pneumonia, first emerged – in the last 14 days.
One man is being treated in the Royal Victoria Hospital in Belfast – he is thought to have been admitted with a high temperature.
The Scottish government confirmed there were five suspected cases in Scotland.
Prime Minister Boris Johnson’s spokesman said the tests were “purely precautionary”.
It is likely to be several days before tests will confirm whether they have contracted coronavirus or not.
Wuhan – which has a population of 11 million people – has gone into lockdown, with authorities suspending planes and trains in and out of the city.
The UK is monitoring flights arriving from China as a precaution.
In a statement to the House of Commons, Mr Hancock said that it was a “rapidly developing situation and the number of deaths and the number of cases is likely to be higher than those that have been confirmed so far and I expect them to rise further”.
He told MPs: “The chief medical officer has revised the risk to the UK population from ‘very low’ to ‘low’ and has concluded that while there is an increased likelihood that cases may arise in this country, we are well prepared and well equipped to deal with them.”
He added: “The UK is one of the first countries to have developed a world-leading test for the new coronavirus.
“The NHS is ready to respond appropriately to any cases that emerge.”