Three more people in England have tested positive for coronavirus, bringing the total number of UK cases to 23, the Department of Health has said.

One case is from Gloucestershire, one from Hertfordshire and one from Berkshire, according to the chief medical officer for England, Prof Chris Whitty. Two patients recently returned from Italy and the other from Asia. “All three are being investigated and contact tracing has begun,” Whitty said.

The news came as health ministers were working to establish how a British patient on Friday became the first to contract the illness within the UK, as the government began to announce emergency legislation to avert a feared economic meltdown.

A man from Surrey is the first UK citizen to have tested positive for Covid-19 without having recently been abroad. Officials are working to trace anyone who has been in contact with him.

As many as 23 British people are known to have been infected with the coronavirus so far, with new cases reported in Wales and Northern Ireland. One man who was on a cruise ship in Japan died from the disease.

The Guardian has been told there are fears that a GP may also have been infected. If confirmed, this would prompt particular concern as the doctor would routinely have seen scores of patients over the course of the last week.

It is understood that the surgery where the doctor works is one of 100 practices where patients with breathing problems are now being routinely screened for Covid-19.

Edward Argar, the health minister, refused to confirm the report about the GP. In an interview on BBC Radio 4’s Today programme on Saturday, he said: “It is a new development but the chief medical officer has also said we are still doing the contact tracing around that and we are still looking into the details of that case, so it is probably a bit premature to say more than that at the moment.”

Ex-health secretary Jeremy Hunt, the MP for South West Surrey, tweeted: “Thinking of clinicians, staff and patients at the Haslemere health centre … worrying time but I know local NHS and Surrey council [are] working tirelessly to keep everyone as safe as possible. Thoughts today with new Covid-19 patient and local GP with symptoms alongside their families.”

On Thursday Whitty spoke publicly about the possibility of cancelling sporting events and closing schools for months if necessary to protect the public. But Agar said there was no reason to curtail mass events.

“[Whitty] said decisions on large events and whether they should go ahead will be taken at the time on the basis of the evidence. He’s not saying there is a need for that now,” he said. “Similarly with school closures, he’s been clear there is no reason or need for schools en masse to close. If there are particular incidents, Public Health England and local teams will give advice.”

The Bank of England governor, Mark Carney, has said the expected global economic slowdown caused by the coronavirus outbreak will have a knock-on impact on the UK.

Downing Street is preparing to rush through emergency legislation and an action plan that includes drafting in military medics, and British Red Cross and St John’s Ambulance personnel to help the NHS cope with any escalation in infections.

Schools, councils and the rest of the public sector will be given powers to suspend laws, including health and safety measures, to cope with a pandemic, the Times reported. Teachers and nursery workers will be allowed to have bigger class sizes in cases of widespread staff absences under the measures expected to be introduced next week.

Boris Johnson has said he will convene a Cobra meeting on Monday.