A London Underground train driver on the Jubilee Line has tested positive for coronavirus, Transport for London (TfL) has said.
The driver, based at the North Greenwich depot, had recently returned from a holiday in Vietnam.
It comes as the mayor of London cancelled the upcoming St Patrick’s Day celebrations because of the coronavirus outbreak.
Sadiq Khan said he had been left with no choice but to call off the event.
It was due to take place in Trafalgar Square on Sunday and official St Patrick’s Day events have been held in London since 2002 and attract more than 50,000 people.
Mr Khan said: “London’s Irish community makes a huge contribution to our great city.
“I recognise that the unavailability of key performers and parade participants leaves no choice but to cancel.
“I know this will be extremely disappointing news for so many Londoners and visitors to our capital.”
Mr Khan also warned that “things will get worse before they get better” and “more deaths” were to be expected.
Closing public transport would be “unsustainable”, the mayor added.
The Tube driver is self-isolating, and the train and depot he worked in is being deep-cleaned, TfL said. The driver said he had not worked in any public-facing job since returning from Vietnam.
A spokesman added: “The safety of our staff and customers is our top priority and we are taking all necessary precautions.
“The areas where the driver worked are being cleaned, including the depot and the trains, in line with guidance from Public Health England with whom we are working closely.”
Find out how many confirmed cases of coronavirus there are in your area:
Elsewhere, King George Hospital in Goodmayes and Queen’s Hospital in Romford have had to suspend in-patient surgeries in order to “protect” patients from the coronavirus outbreak.
Earlier Barking, Havering and Redbridge University Hospitals NHS Trust confirmed that a patient in her 60s, who tested positive for Covid-19, died at Queen’s Hospital.
The trust said it would still carry out cancer and emergency surgeries, and said it was only allowing parents to visit neonatal intensive care unit and all children’s wards.
Heathrow Airport said any passengers flying to the US would have their immediate travel histories checked by their airline before leaving the UK.
The move will come into place from 04:00 GMT on Saturday, and comes after the US government announced there would be a travel ban on 26 European countries.
All Premier League football matches have been postponed until 3 April at the earliest, following an emergency meeting in central London.
Arsenal manager Mikel Arteta and Chelsea winger Callum Hudson-Odoi have tested positive for the virus and are in self-isolation.
The English Football League (EFL) has suspended matches in the Championship, League One and League Two, also until 3 April. But National League fixtures are still expected to go ahead.
King’s College London has cancelled its spring exams and all field trips abroad, but said that the university would remain open and teaching would continue.
Universities including Loughborough, Durham, Manchester Metropolitan and the London School of Economics have all said they will offer online teaching instead of face-to-face lessons.