A woman who flew into London from China a few days ago is being treated for coronavirus, bringing the total number of UK cases to nine.
Chief medical officer Chris Whitty said the woman was transferred to a specialist NHS centre at Guy's and St Thomas' in central London.
Prof Whitty said the patient had contracted the virus in China.
Sources say she developed symptoms after landing at Heathrow, called NHS 111 and then tested positive.
It comes after Prof Paul Cosford, from Public Health England, earlier told the BBC that more UK cases were "highly likely".
Meanwhile, all 83 people being held in quarantine at Arrowe Park Hospital in the Wirral have been told their final set of test results for the coronavirus have come back negative, confirming they are free of the virus.
It is expected they will leave the accommodation on Thursday morning, having spent two weeks there in quarantine.
Earlier, British businessman Steve Walsh, one of the nine UK cases of coronavirus, left hospital having fully recovered.
Mr Walsh, a 53-year-old scout leader from Hove in East Sussex, now posed "no risk to the public", NHS England said.
He was the third case of the virus to be confirmed in the UK, following two Chinese nationals testing positive in York.
Mr Walsh contracted coronavirus on a business trip to Singapore and unknowingly passed it on to 11 other people - five of whom then returned to the UK.
Two of them are known to be GPs.
Officials know the pair worked at a nursing home, Worthing Hospital A&E and two GP practices between them.
Public Health England confirmed on Wednesday it has traced and advised all close contacts of the two GPs, including about 12 patients.
A total of 1,750 people in the UK have tested negative for the virus.
