Camilla, the Duchess of Cornwall, has tested positive for Covid-19, days after her husband the Prince of Wales caught the virus, Clarence House has announced.
Camilla, 74, caught the virus for the first time while Prince Charles has tested positive for a second time.
A Clarence House spokesman said: “Her Royal Highness The Duchess of Cornwall has tested positive for Covid-19 and is self-isolating.
“We continue to follow government guidelines.”
It is believed Camilla has had two jabs and the booster.
The duchess carried out a string of engagements last Thursday – the day Charles tested positive.
Camilla described herself as “luckily” negative the same day, saying of her testing regime during a visit to Thames Valley Partnership in Buckinghamshire: “I’ve taken it so many times”.
Concern for the Queen’s health mounted after the monarch was in direct contact with eldest son Charles two days before he tested positive.
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Buckingham Palace said on Thursday that the Queen was not displaying any symptoms, but did not confirm whether she had tested positive or negative, citing medical privacy.
The 95-year-old spent time with Charles last Tuesday when the prince was carrying out an investiture on her behalf at her Windsor Castle home.
The Queen recently announced she wishes for her daughter-in-law to be called "Queen Consort" when Prince Charles is crowned King.