Prince Albert of Monaco has become the first monarch to contract the coronavirus.
He is the first monarch and first head of state to test positive for Covid-19.
In a statement reported by the Associated Press, the palace in Monaco said there was little concern for the 62-year-old’s health.
Prince Albert was recently in the UK, and joined the Prince of Wales for a round table discussion at a WaterAid event.
Albert is being treated at the Princess Grace hospital, named after his mother who was best known as Hollywood star Grace Kelly before her marriage.
In the statement, the ruler urged residents of his tiny Mediterranean principality to respect confinement measures.
Earlier this week Karl von Habsburg, whose ancestral title is archduke of Austria, confirmed he has contracted Covid-19.
He told Austrian network OE24: “It's annoying, but I'm fine. It's not the black plague.
“I thought it was the usual flu. When a friend called me that he had a positive test at a congress in Switzerland, I was also tested.”
Prince Albert is a long term supporter of WaterAid and was at the same event as Prince Charles and several others in Kings Cross on 10 March.
At the event, Charles called for a similar response to climate change as to the coronavirus outbreak.
He had been careful to follow government advice, and stopped shaking hands, instead using a namaste gesture to greet others.
Albert is the second child of Prince Rainier of Monaco and Princess Grace. He became a five-time Olympic bobsledder and in recent years has been a global environmental campaigner.
Fluent in English and French, Albert graduated from Amherst College in Massachusetts with a degree in political science in 1981, and is a member of the International Olympic Committee.
He and his wife, the former Charlene Wittstock, have twin children.
Monarchies around the world have been impacted by the pandemic.
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The Queen continued her audiences at Buckingham Palace on Wednesday but held her weekly audience with the prime minister on the phone.
She is likely to continue holding the meetings by phone for the foreseeable future.
She left London a week early and headed to Windsor Castle for Easter Court. But many of her engagements will be cancelled or postponed.