The 20th patient in Britain to test positive for coronavirus caught it within the UK, health officials have confirmed.

Chief medical officer Professor Chris Whitty said it was not yet clear if the illness had been passed on from somebody who had recently travelled abroad.

Health officials have begun efforts to trace anyone who may have come into contact with the patient.

Prof Whitty said: "One further patient in England has tested positive for Covid-19.

"The virus was passed on in the UK.

"It is not yet clear whether they contracted it directly or indirectly from an individual who had recently returned from abroad.

"This is being investigated and contact tracing has begun.

"The patient has been transferred to a specialist NHS infection centre at Guy's and St Thomas."

The news comes after a British man became the first UK citizen to die from coronavirus.

The man, who was on board the Diamond Princess cruise ship was the sixth person from the vessel, which has been quarantined off the Japan's coast amid the outbreak, to have died.

In Scotland, 500 people have been tested for the virus but there have been no positive tests so far.

Scotland is now the only part of the UK with no known cases of the virus, with England, Wales and Northern Ireland all affected.

Meanwhile, Prime Minister Boris Johnson said containing Covid-19 was now the Government's top priority.

He told reporters that he had met with the Health Secretary and chief medical officers to discuss the preparations.

He said: "On the issue of coronavirus, which obviously is a great concern to people, I just want to reassure everybody and say that the NHS is making every possible preparation.

"As you can imagine, the issue of coronavirus is something that is now the Government's top priority.

"I have just had a meeting with the chief medical officer and Secretary of State for Health talking about the preparations that we need to make."

Mr Johnson said that people were right to be concerned about the virus but the best thing they could do was regularly wash their hands with soap and water.

He added: "I just really want to repeat the advice of the chief medical officers, which I think is the best thing to get across - the most valuable thing we can all do to prevent the spread of the coronavirus is to wash our hands for 20 seconds or more with hot water and soap.

"That's the best single piece of advice we can give.

"I think people are right to be concerned and they are right to want to take every possible precaution, and we will in the course of the next few days be issuing further advice about how to respond and how we will be deal with any potential outbreak."

When asked if the Government should have repatriated people from the quarantined cruise ship Diamond Princess sooner, Mr Johnson said it had been following the "best medical advice".

He said: "We were following the best medical advice.

"We very much regret the loss of life of the individual concerned but we think that the best thing to do is not to move people around too much in the current situation.

"Not to repatriate unless you can be absolutely sure there is not going to be a spread or contagion to this country, so that's the principle we are adopting."

People who travelled on public transport between Dublin and Belfast should not be concerned about the risk of Covid-19, the Public Health Agency (PHA) in Northern Ireland has said.

Anybody in close contact with Northern Ireland's first Covid-19 patient has been contacted, health authorities north and south of the border said.

The woman travelled through Dublin Airport on her way home after flying with Aer Lingus from northern Italy with a child.

Dr Jillian Johnston, consultant in health protection at the PHA, said: "All stages of the individual's journey were identified and those who came into closest contact have been traced and contacted with public health advice and guidance.

"I would emphasise that members of the public who have travelled between Dublin and Belfast using public transport need not be concerned.

"Contact tracing is an effective and efficient method carried out by the PHA to help prevent the further spread of infections such as Covid-19."