Britain's 95-year-old Queen Elizabeth II tested positive for Covid-19 on Sunday but her symptoms are "mild" and she intends to continue with light duties at her Windsor Castle residence, aides said.
The news comes after Prince Charles, the queen's eldest son and heir, tested positive on February 10, two days after meeting his mother at Windsor.
No information was given then on whether Queen Elizabeth -- who this month marked 70 years on the throne -- had taken any Covid tests herself.
She resumed in-person audiences at the castle last week, but complained to one attendee of suffering from stiffness and was photographed holding a walking stick.
"Buckingham Palace confirm that the queen has today tested positive for Covid," a statement from the palace said.
"Her Majesty is experiencing mild cold-like symptoms but expects to continue light duties at Windsor over the coming week," it said.
While normally secretive about the queen's health, the palace has previously confirmed she is fully vaccinated against Covid-19.
Britain's Press Association said "it is understood a number of cases have also been diagnosed among the Windsor Castle team".
There was no immediate comment from Prime Minister Boris Johnson. But his health secretary, Sajid Javid, tweeted: "Wishing Her Majesty The Queen a quick recovery."
Keir Starmer, leader of the main opposition Labour party, also tweeted his best wishes for "a speedy recovery", adding: "Get well soon, Ma'am."
On the eve of the 70th anniversary of her accession on February 6, the monarch held a reception for locals at Sandringham, her estate in eastern England.
It was reportedly her largest in-person public engagement since an unexplained health issue saw her spend a night in hospital last October.
The queen's second son, Prince Andrew, settled a sexual assault civil lawsuit in the United States last week, reportedly for £12 million ($16.3 million, 14.3 million euros) -- which newspapers claim she will partly fund.
Meanwhile police in London have said they are investigating claims that a Saudi tycoon was offered UK honours in return for donations to Prince Charles' charitable foundation.
The queen, whose husband Prince Philip died aged 99 last April, has spent much of the coronavirus pandemic at Windsor Castle, with a reduced number of household staff dubbed "HMS Bubble".
Respecting the government's then rules on Covid distancing, she sat alone at Philip's funeral.
