Britain's Prince Charles, Prince of Wales (center) attends the official commissioning ceremony of HMS Prince of Wales in Portsmouth, south England on Tuesday. HMS Prince of Wales is the second of the Royal Navy's QE Class aircraft carriers, built by the Aircraft Carrier Alliance. Photo: AFP

Prince Charles, the eldest son and heir of Britain's Queen Elizabeth II, is no longer in quarantine after showing mild coronavirus symptoms, his office said on Monday, as scientists said strict measures put in place across Britain to limit close-contact transmission could be having an effect.

"Clarence House has confirmed today that, having consulted with his doctor, the Prince of Wales is now out of self-isolation," it said in a statement.

The 71-year-old prince, whose age put him among the most-risk category for the disease, is said to be in good health and abiding by government health guidelines.

Royal officials announced on March 25 that Charles was in self-isolation at the queen's sprawling Balmoral estate in northeast Scotland. He tested positive on March 24.

His wife, Camilla, Duchess of Cornwall, 72, tested negative.

Both were seen in video footage Thursday joining in nationwide applause for doctors, nurses and other healthcare professionals dealing with the outbreak.

Clarence House said doctors believe Charles became contagious on March 13 - a day after last meeting his mother.

The 93-year-old queen has been staying with her 98-year-old husband Prince Philip at Windsor Castle, 820 kilometers south of Balmoral, since March 19.

Given their age - and Prince Philip's stay in hospital at Christmas - the prince's diagnosis prompted questions about their potential exposure to the virus.

But Buckingham Palace said that the queen was "in good health," and her husband was not present when she last saw Charles.

Prime Minister Boris Johnson, 55, has also tested positive for the virus and is currently in self-isolation, as is his chief adviser Dominic Cummings, and two other cabinet ministers.

The head of the National Health Service (NHS) in England, Simon Stevens, said more than 9,000 people were being treated in hospitals - a 50 percent increase since Friday.

Britain on March 23 began a three-week lockdown of non-essential shops and services to limit the close-contact spread of the virus and reduce the burden on the overstretched state-run NHS.

About one in four NHS doctors are off work sick or in isolation, according to the Royal College of Physicians. One in five nurses have been affected, the Royal College of Nurses said.

AFP