The queen and Prince Philip are now being looked after by a very small group of their most trusted and longest serving aides, a source tells ET.
The queen "remains in good health and is following all the appropriate advice with regards to her welfare," the source says.
ET has also learned that only essential staff are having contact with the queen -- and extended family members and those working for the 93-year-old monarch are kept at a distance following social distancing protocols that have been put in place to protect the queen and other British citizens.
Prince Philip, who had been living at Wood Farm in the Sandringham estate, is in Windsor with the queen ahead of the Easter holiday. The queen is expected to stay at Windsor Castle, rather than return to Buckingham Palace, while the coronavirus pandemic continues.
It was revealed on Wednesday that Prince Charles -- the eldest son of Queen Elizabeth II and next in line to the British throne -- had tested positive for the illness that is sweeping across the globe.
At the time, it was reported that the 71-year-old Prince of Wales was showing "mild symptoms" but was said to be in "good health." His wife, Camilla, the Duchess of Cornwall, was also tested, but did not have the virus. They are both self-isolating at their home in Scotland.
The palace said in a statement at the time, "It is not possible to ascertain from whom the prince caught the virus owing to the high number of engagements he carried out in his public role during recent weeks. He has not been to the hospital. His symptoms are mild and [he] is in good spirits."
Buckingham Palace previously revealed that Charles was last in contact with his mother, Queen Elizabeth II, on March 12.