A Buckingham Palace aide reportedly tested positive for Covid-19 while the queen was still in residence.
According to the British media, the palace staff member was diagnosed with the coronavirus last week, just before Her Majesty moved to Windsor Castle.
All members who were in contact with the aide were told to self-isolate, Mirror reports.
"The worker tested positive before the queen left for Windsor [Castle]," a royal insider revealed.
"The palace has 500 members of staff so, like any workplace, it’s not inconceivable it would be affected at some stage."
It’s not yet known if the 93-year-old came into contact with the infected aide, who’s not been named yet, Page Six reports.
Buckingham Palace has refused to comment on the case but said it’s taking all precautionary measures to ensure the health and safety of its staff.
"We wouldn't comment on individual members of staff. In line with the appropriate guidance and our own processes, we’ve taken the necessary actions to protect all employees and people involved," a palace spokesperson told NDTV.
The queen and Prince Philip are in good health and self-isolating in Windsor Castle, according to the palace.
Last week the queen released a statement urging people to practise social distancing.
"Many of us will need to find new ways of staying in touch with each other and making sure that loved ones are safe. I am certain we are up to that challenge," the statement read.
"We are enormously thankful for the expertise and commitment of our scientists, medical practitioners, and emergency and public services; but now more than any time in our recent past, we all have a vitally important part to play as individuals – today and in the coming days, weeks and months.”