The Prince of Wales is 71, which puts him in one of the high-risk categories, according to U.K. government guidance.
Camilla, the 72-year-old Duchess of Cornwall, has also been tested but does not have the virus, PA Media reports. The couple is currently self-isolating at home in Scotland.
“He has been displaying mild symptoms but otherwise remains in good health and has been working from home throughout the last few days as usual,” a Clarence House spokesperson said.
Charles’s last public engagement was on March 12, but he did have a number of private meetings with some individuals, all of whom have been made aware.
A source said his doctor’s most conservative estimate was that he was contagious on March 13, which is after he last visited the Queen.
The tests were carried out by the British National Health Service in Scotland.
“In accordance with government and medical advice, the prince and the duchess are now self-isolating at home in Scotland,” the Clarence House spokesperson said.
Clarence House said it was “not possible to ascertain” how Prince Charles contracted the virus “owing to the high number of engagements he carried out in his public role during recent weeks.”
Britain’s Press Association, citing a source, said the prince and the duchess remained in good spirits, and that Charles was not bedridden.
Medical advice is that his case is unlikely to escalate into a more serious one.
Queen ‘in good health’
Prince Charles has spoken to his sons, Prince William and Prince Harry, as well as Queen Elizabeth, who is 93.
“Her Majesty The Queen remains in good health,” a Buckingham Palace spokeswoman said. “The Queen last saw The Prince of Wales briefly after the investiture on the morning of March 12 and is following all the appropriate advice with regard to her welfare.”
Buckingham Palace said Queen Elizabeth remains at her home in Windsor with the 98-year-old Duke of Edinburgh. Prince Philip was not with the monarch when she last saw Charles.
Earlier this month, Prince Charles attended an event with Monaco’s ruler, Prince Albert, who later tested positive for COVID-19. The British royal is not believed to have shaken hands with Albert at the WaterAid Summit in London on that day.
Prince Charles is currently the heir to Queen Elizabeth, which makes him next in line for the British throne. Prince William, the Duke of Cambridge, is next in line after him.
With files from The Associated Press