The worker was sent home over the weekend after their PCR test came back positive, The Sun reports.
"All the staff at Balmoral are tested for COVID daily and on Saturday this person showed up positive," a source told the publication. "They were sent home and the staff canteen and bar were shut. They're on a separate block on the estate."
The source went on to add the workers have been told to wear masks and socially distance and that for now, workers will continue serving food to the Queen and her family members.
"Although Her Majesty is 95 and has been double jabbed, the feeling is she still has to be careful, yet she's determined to carry on as normal. She does not want to overreact."
The Sun reports the monarch did not attend church as per usual on Sunday, which the publication said is likely due to her having been tested for COVID-19 and waiting to see her results.
The Queen is spending her first summer holiday at Balmoral without Prince Philip, her beloved husband of 73 years, who passed away at age 99 in April. She has started to be joined by family members, including Prince Charles, Duchess Camilla, Sarah Ferguson, Prince Andrew, Princess Eugenie and Jack Brooksbank and their son, August. She is expected to welcome other relatives, including Prince William, Duchess Kate and their children, along with Zara and Mike Tindall and their three kids, later in August. Prince Edward and the Countess of Wessex are also likely to make a visit.
As mentioned, the royals are tested regularly for COVID-19. At the beginning of the coronavirus pandemic in March 2020, the Queen and Philip were moved to Windsor Castle, though the couple did spend a few weeks at the Scottish estate last year.
Traditionally, the Queen spends the end of summer and early fall at Balmoral before leaving in October. In addition to family members, she also typically receives people such as the U.K. prime minister and other international dignitaries. The Queen is expected to return to Windsor, where she has been living full time, after her time at Balmoral ends.
Earlier this year, Kate had to self-isolate after she had contact with someone who later tested positive for COVID-19. The illness has also affected the royals: Charles recovered from the virus in March 2020, while William was reported to have had it soon afterward. Princess Michael of Kent also recovered from COVID-19 in November 2020.