Two patients from the same family in England have tested positive for coronavirus, the first such cases in Britain, health chiefs said on Friday.

They had warned that the United Kingdom was highly likely to have cases of the new coronavirus, which first emerged in China's central province of Hubei and has killed 213 people so far.

"The patients are receiving specialist National Health Service (NHS) care and we are using tried and tested infection-control procedures to prevent further spread of the virus," England's chief medical officer, Chris Whitty, said.

Whitty said the two infected patients had been transferred to a specialist infectious disease unit in Newcastle, northeast England. He said it could turn out to be a relatively minor infection as there was only a 2% mortality rate.

Staff, other patients and the general public would not be at risk, he said and health officials were tracing those who had been in close contact with the pair.

Whitty also said they were extending their advice so that anyone who had returned from China should "self-isolate" if they developed symptoms of any kind.

On Thursday, Britain raised the perceived risk level to the country from an outbreak of coronavirus in China to moderate from low after the World Health Organization (WHO) declared a global health emergency.

A plane carrying 83 British and 27 foreign nationals from Wuhan, the capital of Hubei, is due to arrive in Britain later on Friday before continuing to Spain.

The returning Britons will be quarantined for 14 days at an NHS facility in northwest England.

"What we wish to do is make sure they are in one place near very good infectious disease and other medical services in the event they need it," Whitty said.

"What we hope is that all these people will have 14 days isolated from the general public but not in the sense of solitary confinement and then they will be able to be released without any symptoms at all," he said.